If it's iPhone, then you need to use the Damus app from the TestFlight AppStore, i.e. the beta version. There are only 10k beta slots, so if you don't already have it, you're out of luck for now. But it'll pop up in the regular AppStore soon, for sure

If you're lucky enough to be in the beta, then go to your Damus profile, then Edit, and put an LNURL into the "Bitcoin Lightning Tips" field (LNAddress/LNURL both work I think).

You can get an LNURL from the Wallet of Satoshi App: Go to "Receive", then hit the "@ Lightning Address" button in the upper right. A QR code will appear. Below the QR code will be an LNURL string. Copy that and paste it into Damus.

Alternatively, you can copy the yellow email address above the QR code. That's the LNAddress. LNURL seems to work best, however, as it's compatible with more wallets. Or so I've heard.

If you're NOT on the Damus beta:

Just keep checking the AppStore version. There will be a zap button next to the "like/shaka" button