I want to download the new updates I think to the 10.9 but our mac was given to us and when it comes to the last page it asks for the user name and password but this mac was wiped clean. How do I find out this info so I can get iPhoto?

I want to download the new updates I think to the 10.9 but our mac was given to us and when it comes to the last page it asks for the user name and password but this mac was wiped clean. How do I find out this info so I can get iPhoto? To be honest I'm not even sure what type of Mac I have and don't know how to find out what kind it is

I'd also like to make address labels and don't know where to find that either