combining apple products

Set up the same iCloud account on all three, and enable the data you want to sync. On your iOS devices, go to Settings>iCloud, sign in with your Apple ID to create your account and turn on the items you want to sync. If desired, you can also turn on Find My iPhone (iPad), Photo stream (in Photos), and iCloud backup (in Storage & Backup). On your Mac, go to Systems Preferences>iCloud and sign in with the same ID, then check the data you want to sync. See http://www.apple.com/icloud/setup/.

You can import them from the camera roll on your iPad to your computer (see http://support.apple.com/kb/HT4083), then sync them to your iPhone by selecting them on the Photos tab of your iTunes sync settings and syncing. Or, you can transfer them between your devices/computer over your wifi using an app like PhotoSync.