How to transfer the items from my iphone to my itunes library?

I'm trying to update my iphone but whenever I connect the iphone to my laptop it says that first I'm gonna have to transfer the purchased items such as games into my itunes library or I may lose them all. I'd be glad if you could help me out.

Plug in your iPhone, then when it shows up on the left hand column, under devices, right click on your iPhone (example Mary's iPhone). You'll get a drop down box of options, one of which is transfer purchases. You want to click on that one. Also, you'll have to make sure your computer is authorized to use the apple id on the iphone, first. If it's not, it will prompt you to, then you'll have to reclick to transfer purchases.