Can you specify what you mean by accessing your friends website?

If you're a control panel user you can log in to the control panel via slug.nationbuilder.com/admin.

The slug is the name of the account. If you're not a control panel user, but just want to log in to the front of their website, there should have a log in normally located at the bottom of the page.

If they've customized, it may be located elsewhere. Please let us know.