Maybe we should set up a video conference or something! LOL.
Two ways to do it:
1) Grab the markers on the vertical and horizontal rulers and drag them, being careful not to drag them too far or pull them out of the current page view (which makes them scroll very quickly like in MS Word)
2) Clicking on either the MB itself or the dark grey background in the window (ie. next to the site page itself) will bring up the ever-varying properties palette for the MB. In which you can set the figures for left, top, right and bottom areas. My preferred method by far.
Saying that, I don't use MBs much now, except for holding common content such as copyright notices, etc. that reside at the bottom of each page. The rest of the content gets re-created on each page to allow lots of customisation! For a while, I made different MBs for groups of pages, but that only works efficiently in some layouts.