When I go to my site I see pages from my old host.

When you create a hosting account using an existing domain name you have to change the name servers for the domain. (A change of address if you will)  

If you look at the account information email that you were sent there is a green bar on the right side.  ¾ of the way down you will see a section for the name servers.  These are the name servers for the server your account is on.  Log into your account with your old host or registrar and update the name servers.  This change will kick in within 2 – 4 hrs in most cases but can take up to 24 hrs.

Refer to questions for changing name servers with specific registrars