You can send gifts at the gift center by clicking on the gift box in the left bar on the map, under your passport.
Clicking the gift box will open the Gift Center
Pick the gift you want to give. By clicking 'SEND', all your available friends & Buddies will appear.
Please note that you can send each friend 1 gift every 24 hours, so only friends that have not received a gift from you in the last 24 hours will be displayed.
As a general notion,
Facebook tab - displays all of your Facebook friends that have joined Bingo Drive.
Buddies tab - displays all the players that you have become buddies with.
Online tab - displays friends & buddies from both tabs that are online.