Why can’t I get my emails on my MacPro Air

No such thing as a MacPro Air. It's either a Mac Pro (large desktop computer), a MacBook Pro (larger laptop) or a MacBook Air (smaller laptop). 3 very different things.

To add emails to a computer, open the Mail App, then go to the Mail Menu->Accounts, click on the account type on the right side, and follow the onscreen prompts to add the email accounts.

Don't know. Have you correctly configured your email client? What happens when you try?