recently bought an IPhone 4s and activated it through my husbands ITunes account. Now my husbands email address on my phone when attempt to access Apple. How can get his email address off my IPhone so can replace it with mine

I recently bought an IPhone 4S.  My husband activated it for me through his ITunes account.  Subsequently, I created my own Apple account.  Here is the problem.  When I attempt to access ITunes or Apple apps my phone still shows my husbands email address and requests his password.  I want to get that changed so it reflects my email address and password but can't seem to do so through the settings mode.