New phone im switching to is not updated

My phone died to day iphone5c, water damage, I heard a call come through and sent to voicemail but the screen is shot. I switched it over to my mother-in-laws old iphone5. I erase it, switched sim cards, and was in the process of restarting it and syncing my cloud. Well apparently I forgot to make sure the phone is up to date on the system updates before I did all of that. Now I'm stuck in the "Hello" set up mode and can't go anywhere else to try to update it. My cloud is iOS 8.4 and the phone is at iOS 7.1.2 Is there anyway around this? Or someway to fix this?