The Basics

Click the Login in the lower right corner of any page.  Log in using the username and password you've been given.

The Admin Menu will be visible in the upper right corner of your site.  It floats on the page so you can always get at it.  If the Admin Menu is covering the spot where you need to work, make the window wider to give it more room.

Save! Save! Save!
When you log in to work on the site, you log in using protection provided by the server.  The server will log you out after a period of inactivity.  If you forget to save and then go back to continue working, you may get a message You have to log in to access the area you requested.  Any changes you made will be lost.  So remember to save often - and especially if you have to interrupt your work.

Refresh
For some operations, you'll need to click Refresh to see the results.  And if you are making changes but they don't seem to be working, always try Refresh.  The Refresh icon is a round arrow pointing clockwise.  You can also use the keyboard shortcut F5.

Use multiple windows.  
When you are working on the site, it may be helpful to use two windows - or even more.  Open the site in your browser.  Then open another browser window by right-clicking the browser icon in the toolbar.  In this window, log in and do your work.  When you want to see the results, go back to the other window and refresh.

Super Tip: Alt-Tab 
The keyboard shortcut to switch windows is Alt-Tab.  Hold the Alt key and press Tab repeatedly until you see the window you want.  Then let go of Alt.  Alt-Tab remembers which window you were in last.