My dad gave me his iphone 5c, was just gonna switch over it but it keeps saying sim is in use. So guess have to buy a sim....so do I just go in, get sim & it's on my account or have to go through other process?
" ... it keeps saying sim is in use. "
Did you try to update your sim through self serve?
If your current phone and the iPhone 5c use same size sim card, you just put your sim into the iphone and reboot it.