How to get a new ID and Password for Apple Iphone4s?

The problem is that one of my cousins gave me her iphone which was in her use first, and later she went abroad, now the problem is that when ever I try downloading something on Iphone it asks for a password, neither I nor do my cousin remember the password. And now I can't download anything. What should I do? How do I get a new ID and password which I can make on my own and can use it for downloading stuff?

Your cousin can reset the password by going into - https://iforgot.apple.com/iForgot/iForgot.html

or

If you want one for yourself then go into - https://appleid.apple.com/...lang=en_UK

Have a new iphone and can't log in with the id and my password