Start it, instruct it

You did this once with the Claude CLI. Same moves for Codex.

Make a fresh practice folder, step into it, and start Codex:

mkdir codex-practice
cd codex-practice
codex

mkdir and cd are your terminal skills. codex on its own starts a session right here in codex-practice. That folder is now Codex's world for the session: empty, safe, yours.

Codex shows you its own prompt, waiting for an instruction. It looks a little different from the Claude CLI's, but the idea is identical: it's ready, and nothing happens until you type something and press enter. To leave the session later, you type /exit or press Ctrl and C, the same exits you already know.

Give it a real first instruction

In the Codex session, type a plain-English instruction and press enter. Use one that's small, concrete, and easy to check:

Create a file called toolkit.txt with two lines: one line naming a
task I'd use the Claude CLI for, and one naming a task I'd use Codex
for.

That's it. No code, no flags. A sentence describing the outcome, exactly like briefing a coworker, exactly like the Claude CLI. The briefing skill you've been building does not reset between tools.

Worst case, you don't like the file and you delete it with rm toolkit.txt. Press enter on your instruction and watch what Codex does. The next step walks through it, and it should feel familiar.