Once you have set up your Family Sharing master device adding an additional person is very easy. Navigate to Settings > iCloud > Family and tap the "Add Family Member..." panel. This will open a new window. From here just type the email of the person you want to add.
iPad Family Sharing
iOS 8 allows one credit card holder to set up a master account for up to six devices to share all content purchased from iTunes, iBooks and the App Store. The master account holder must approve all future purchases made on that credit card, and members of the Family Plan do not need to share an Apple ID. This allows parents to control purchases made on any family devices, including the iPod touch, iPhone and iPad, and allows families to share content like games or music with other family members.