If you've set up first-generation or second-generation AirPods with your iPhone and your Mac is signed in to iCloud with the same Apple ID, then your AirPods should be ready to use with your Mac.
Ideally, all you need to do is put your AirPods in your ears, click the Bluetooth icon in your Mac's menu bar, select your AirPods from the dropdown list, and click Connect.
If you don't see...