You’ll need a lightning wallet that is able to give you an LNURL address (“Lightning Address”). You’ll also need to share that address with your client for Nostr.

On Desktop, Alby can do it. On iOS or Android, Wallet of Satoshi can give you an LNURL address to put into your Nostr client app.

You need a Lightning Network wallet that supports lnurl. If you want to start the easy way you can install Wallet Of Satoshi. It is not an optimal solution, but for starter and for small amount could do!