It took me a little time to understand it also :)
Lets see if I can explain it - please forgive me if my explanation is rubbish :)
Admin Menu - you should see 5 options:
Admin Multimenu 1
Admin Multimenu 2
Admin Multimenu 3
Admin Multimenu 4
Blocks Admin
Each of the Admin options reffers to a different menu block (1-4).
Click on the first one....
Firstly you want to create a link. Click "New Link"
Title: Give the link the title you wish. Example "Site Credits".
Link: Destination of the link. Example:
http://www.mysite.com/credits.htmHide: useful if you want to remove a link while you change something - leave set to NO
Target: I normally leave to "Self" - Other options will create a new browser window. Useful for external sites
Groups: If you want to make this option only visible to webmasters (for example) just select webmasters. For all people on the site - click on all (remember to hold Shift).
Submit your choices.
Repeat for each link
blocks admin
This lets you see who can see the links, and who can alter them.
The top half lets you go into the block menu for each menu block. You can change the name of each menu block here, set it to visible, control what pages it is seen in and so on - the same as with standard blocks.
The tick boxes below:
Tick all the options you want for webmasters.
Registered users - normally only the options from the second line (ie - tick the menu you want them to see)
Anonymous - normally leave unticked (but you can tick what you wish)
Then submit.
That should do it :)
I hope that was of some use at all.