I just got a new computer MacBook pro and would like to access my previously purchased music. However, when I try I get the message that I need to authorize the computer from the account menu, but I can't figure out how to do it

See the following from Authorize or deauthorize your computer for iTunes Store purchases - Apple Support

How to authorize a Mac or PC

Before you authorize a Mac, update it to the latest version of macOS. On a PC, update to the latest version of iTunes for Windows.

1. On a Mac, open the Music app, Apple TV app, or Apple Books app. On a PC, open iTunes for Windows.
2. Sign in with your Apple ID.
3. In the menu bar on your Mac or PC, choose Account > Authorizations > Authorize This Computer.
4. If you're asked to authorize your computer again, it won't use a new authorization. Apple ID uses the same authorization for the same computer.