You can send gifts to your friends using the menu for trading lives. To get there, tap on the bar with the heart icon in the top right corner of the screen. A menu will appear with two buttons: Ask and Send.
Tap the Send button to send lives to friends. A window will pop up with a list of friends who you may send lives to. Select as few or as many friends as you want and press Send. A Facebook window will then appear. Press the Send button here too.
You can also easily send lives to the friends who have requested them from you. If you have requests for lives, a heart icon appears on the News tab. When you open this tab, you will see the friends who have asked you for lives. Tap the Send button to give them extra lives.