When you open your friend’s profile page, you will be able to see if you can send them a gift if  this symbol appears:
Tapping on it will send your friend a gift.

If you have already sent that particular friend a gift that day, or they have already received three gifts that day, the symbol will not be visible and you won’t be able to send them a gift until the next day.

When you wish to send a friendship upgrade token, if the friend you want to upgrade is eligible you will be able to see this symbol on their profile page:
Tapping on it will upgrade your friendship with them.