Firstly... Congratulations on your New iPhone.
I am planning to give my iPhone 4s to my mum as I got my iPhone 5s today.
How do I add another account in iTunes so that each phone has an entirely different content?
Have a read here...
And See Here... http://support.apple.com/kb/HT1495
Create a New User Account for each User.
Then Each user will have their own iTunes library..
You may also find this Video of Value > Click.. Here-
I wanted to have two different Apple ID's for each
Apple ID FAQs > http://support.apple.com/kb/HT5622