iphone not recognizable in itunes

Hey guys,

So I resetted my Iphone 6 as a friend told me I could get rid of all the documents &... on my phone as it took pretty much space on it. Now I have a big problem. When I put my phone via usb on my computer my phone only recognizes that it's charging but on my itunes my phone can't be seen, I really need my itunes to get on my backup to get all my stuff back.

please help I'm sooo frustrated as I'm already trying to figure it out for about 2h straight.