"Invalid OAuth token" when making a request

These instructions are correct.

Normally for script based operations you would generate a Client Credentials token as outlined here

But the type of token needed will depend on the endpoint you are calling, for streams/followed you will need a user access token with permission from the user 141981764 to read their data

Which is This kind of token instead

or

If you followed the guide and generated a token, you generated an App Access Token.

An App Access Token cannot be used to call the streams/followed API that needs a user token

With the scope user:read:follows

This will require a webpage that you redirect the user to, to grant permission between their account and your own ClientID