Need to download apps on iphone that isn't mine?

Okay so basically i'm grounded at the moment. So i don't have my phone or ipod. So i took my grandpa's old iphone 4 without him knowing, and i need to download apps but i don't know what the password is. Can anyone help me find a way to get into the account without the password?

Of course you can't do that. That's why there are credentials for it in the 1st place.