Q: How do I replace a device on itunes?

Hey Sandra,

Congratulations on your new iPhone 6! I interpret your question in one of two ways. The first is getting your information from one device to the other. If that is the case, I would take a look at the first article below to walk you through backing up your iPhone with iTunes or iCloud and then when setting up your iPhone 6 you will have the option to put that back up on there. 

If you are referring to actually activating your new iPhone, then take a look at the second article to walk you through that. You may need to contact your carrier for some assistance depending on your situation .   

Back up and restore your iPhone, iPad, or iPod touch using iCloud or iTunes

https://support.apple.com/en-us/HT203977

Get help activating your iPhone

https://support.apple.com/en-us/HT201407

Take care,

-Norm G.