This guide may still work but not yield the token you want. Refer to the New guide for another method

Guide to obtain your Oculus Token
For Oculus downgrader and other applications
Important
Your token is something private. Everyone who has it can download apps, send messages, ... with your name.
But then the question comes why do I give it Oculus downgrader? Oculus downgrader needs to authenticate the download with oculus so it needs your token. After you entered the token it gets stored locally on your PC and is ONLY shared with Oculus servers to proof that you own the game.
Step 1: Sign in
Open https://developer.oculus.com/manage and sign into your Oculus/Facebook account.
Step 2: Open developer tools
Chrome:
On https://developer.oculus.com/manage hit ctrl + shift + i and go to the Application tab

Step 3: Copy the access_token
Next click on Cookies (1) then https://developer.oculus.com (2) and then oc_www_at (3). You can then copy your token (4) and validate it via the box below.

Validate token
You can then paste your token with ctrl + v into Oculus downgrader.