You’ll want to setup a Lightning wallet. Wallet of Satoshi is the most popular and easy, would suggest that. Then take your Lightning address and put it into your profile settings.
Discussion
OK, I set my wallet in the Damus settings.
You e managed to zap me but I don’t have the ability to sap you yet. Put your Lightning address into your profile settings.
Your wallet Lightning address you can find when you hit ‘receive’ in the wallet and it’s the thing that looks like an email, like ‘funding@walletofsatoshi.com’
The field is under your profile ‘edit’ then ‘Bitcoin Lightning tips’.
Then a bolt will appear next to each post you make and on your profile and you can zap people. Long press for custom amounts.