how do i set up a 2nd administrator account on my mac book pro

System preferences > Users&Groups ...

click the lock and authenticate to open the lock

click the Add [+] under the left pane

select New Account : Administrator and enter the rest of the information

click (create user) button.

Go to System Preferences > Users and Groups, click on the Lock icon and type your admin password, click on the add button (+) and select Administrator on the New Account dropdown menu. Set a password and that's it. Now you can alternate both while logged in to your main account or when you turn up/restart.

See Set up users, guests, and groups on Mac - Apple Support

On your Mac, go to System Preferences > Users & Groups. Click on the lock and type in your password, then click the plus to start creating the account and change the "New Account" option to "Administrator". After that, just follow the prompts to continue creating the account. If you run into other issues, see this: https://support.apple.com/guide/mac-help/set-up-other-users-on-your-mac-mtusr001/mac.

Hope this helps!