To send lives to friends, you will need to log in with a Facebook account. After, tap the Lives counter on the upper left corner. This will bring up a page where you can ask friends to send lives or send lives to friends. Tapping the "Send" button will allow you to select friends or send lives to all of them.
Another way to send lives is by accessing your Messages by tapping the letter button on the upper right. Then tap the "Send Hearts " button on the bottom, which will bring up the "Send Lives" page.
You can also send lives by bringing up the Map Overview page, which can be accessed by tapping the map button on the upper right. Then scroll down until you see a friend and tap the button with the red heart and green arrow on the right to send a life.