Although your words are confusing,but i think i get what are u trying to say.

1) connect your iphone to the computer..then open itunes.
2) if it's a new computer,then u need to key your apple ID n passwrd in order to give authorization for the iphone.
3) then,right click 'Devices' on the left tab,select 'Transfer purchases' first..this will copy any apps that doesn't included yet on your library..if u have a lot of apps n its the 1st time,it could be awhile..wait until it finishes.
4) finally,right click again 'Devices',this time select 'Backup'..this will store your contacts,photos,videos(not sure about messages) n any original apps from your phone to the computer..let it be for another moment until it finishes,

So,after each time u update the iOS,right click 'Devices' n select 'Restore from backup'..this will retrieve the 'Backup' from the computer to your iphone..the most important thing is,BACKUP YOUR IPHONE AT LEAST ONCE A MONTH(OR AT YOUR OWN TIME) COZ U NEVER KNOW WHAT WILL HAPPEN TO YOUR IPHONE