Where in our profile do we add it? Is there a certain format that it needs to be in?

I'm seeing Monero public addresses in profiles, but Garnet doesn't do anything when I tap the address. 

 There's a Monero symbol below every message. Use that one. It picks the address automatically. No special format needed. 

 How can we set the icon to connect to an already existing wallet? 

 not possible i dont think, but if you try and tip other and dont have a balance on Garnet it will ask if you want to use an external wallet on your phone to tip 

 No specific format necessary but look at my profile as an example