Simplest method - create a table with two cells/columns - the left column
becomes your "sidebar".
the other column becomes your main content cell.
Make the table width 100% or whatever you need.
To save doing this for every page, save it as a dynamic web template
(Frontpage 2003), or if you use FP2002 or earlier, save the page as a
"blank" page (name it "template.html" for example), and for every new page
you create, use this blank page as the starting point, and always "save as"
each new page, so you have the blank page left as it is for each new page
you create.