This seems pretty straightforward, but there's one concept that needs to be very clear.
If you do not click on Logout when you are done editing your site, you will remain logged into the site manager on your computer indefinitely. If you are on your home computer, and no one else has access to it, this can be convenient. If you are working on your site on a busy "public" computer in a library, or at your place of employment, this could be disasterous! Ask yourself if there's anyone else that may use that computer in your absence. If so, then log out when you're done editing.