You can grant additional users access to a site.
NOTE: Additional users can only login into to published sites. You must publish your site at least once.
Add an extra user to your site
Click Manage (1)
Click the Users (1) tab and then click on the New (2) button to add an additional user to your account.
You'll need to fill this form to create a new user.
How to open the login box for additional users
Additional users can only login through your published site (i.e. www.mysite.com).
To open the login box, go to the published site and hold down the SHIFT+ ALT + CTRL keys and then type an 'O' (that's the letter o not a zero).
This combination of keys will open the login box so your additional users can start editing the site.