1.
Get the Codex app onto your machine. You go to http://openai.com, find Codex up in the menu, hit the install button and grab the build for Mac or Windows I guess. Whole thing is about a minute, zero setup decisions along the way. A tip from me, even if you have been poking around Codex in the browser, get the Desktop version running from day one, that is where the real usage happens later and you do not want to redo the setup then.
2.
Sign in with the ChatGPT account you already use. Codex runs on the same subscription you are paying for, so Plus, Pro, Business or Enterprise all work, and Free has a limited window right now while OpenAI tests the rollout. A tip, stick to the same email as your ChatGPT so you do not end up juggling two accounts, and if your usage ever tops out switch to GPT 5.4 mini in the chat, gives you roughly two and a half times more runway and the quality holds up fine. You need to give some permissions for read and write, you can change any time or just allow once.. codex will not read your files on the computer if you don't tell him, normally you work in the app folder of codex only!
(optional)
Grab your ChatGPT data first. Pop back into ChatGPT, click on your profile icon, go into Settings, then Data Controls, and press Export Data. OpenAI mails you a zip file within a day or two. Inside you get every chat you ever had plus the stuff the platform knows about you. A tip, kick off the export now even if you are still undecided about moving, the mail takes time to arrive and you want the file ready when the moment comes.(optional)
Get the gist of your ChatGPT history into Codex. Once the mail is in your inbox, open the zip and pull out the chats that actually describe you or your work. Codex has no one click importer, so paste a short personal brief into your first Codex thread, a few sentences about who you are and what you do. A tip, if the full archive feels like too much, three sentences about your job and your style are already plenty, the rest comes out in conversation. Even faster, just ask ChatGPT to write you a short summary of the most important stuff about you in one message, then copy that message straight into Codex, no zip needed.(optional)
Set up a folder for your main topic. Codex lets you group threads together under a folder, so every chat about the same thing lives next to each other. Think one client, one research thread, one side project. Even putting a folder in with just the name of your business counts. A tip, resist the urge to build a perfect structure on day one, start with the one topic you touch the most and add more folders only when they earn their place.
6.
Let Codex get to know you in plain language. This is the part where people raise an eyebrow because there is no configuration involved. You just tell it. Open a new thread and say something like this. I run a small accounting firm, we use QuickBooks and Stripe, keep the tone formal when anything goes to clients. That gets saved and Codex adjusts its responses around it. A tip, feed context in pieces, not in one huge dump, you will naturally add bits as new situations come up anyway.
7.
Get your feet wet with questions first. That input field at the bottom says Ask Codex anything, and for the first day that is exactly how to use it. Ask things you would normally ask ChatGPT, request a draft, think something out loud. Treat it like the familiar chat for a bit before pushing further. A tip, spend a day putting the same question side by side into ChatGPT and Codex, you will figure out on your own which one you reach for and when.
8.
Send Codex a file and tell it what to do. Paste it in, drop it in, upload it, whatever feels natural. PDF, Excel sheet, long email chain, it does not matter. Ask for a summary, a sorted view, a translation, a draft reply. Codex spins up a sandbox in the cloud and works through it, you watch it live in the thread. A tip, start with one small file, the first time you watch Codex handle a real task end to end is when the whole idea clicks in your head.
9.
Ignore the code in the name when it comes to what you use it for. Most of what I hand to Codex has nothing to do with programming. Excel sheets that need sorting. PDFs that need summarising. Research notes. Translation drafts with consistency checks. Inbox triage. Occasional Notion cleanup. Coding just happens to be one of the things it does, not the only thing. A tip, pick three recurring tasks you hate doing by hand and feed them to Codex for two weeks straight, one of them drops off your plate permanently.
10.
Once the basics click, there is a whole power user layer waiting. Six names worth knowing, AGENTS.md, Skills, Hooks, Subagents, Memory and MCP. Nothing you need today, jumping in early is how people burn out. I am putting together a dedicated follow up on exactly these six, it will land here in the sub in the next few days. A tip, when you do dig in, start with AGENTS.md alone, it is the softest learning curve and the one you will end up using every session.
Matthias Meyer
Founder & AI Director at StudioMeyer. Has been building websites and AI systems for 10+ years. Living on Mallorca for 15 years, running an AI-first digital studio with its own agent fleet, 680+ MCP tools and 6 SaaS products for SMBs and agencies across DACH and Spain.
