Double tap zap button

Not wallet of satoshi, within the nostr client. On Damus for example you long press the zap button and add a message in the custom zap dialogue.

Click and hold on the zap button and then type it in the comment box

Most wallets have a "memo" or "note" section. I assume they put it there or it uses that note by default. I'm only guessing tho, I've never used WoS.

Depends on which nostr client you're using

Right here ser (see screenshot). I am using the Damus client for Nostr. So it’s not about which wallet but probably rather about which Nostr client you are using.