Hi Rachel, also if you haven't seen it yet, check out the introduction section of the help file:
http://moi3d.com/2.0/docs/moi_introduction.htm

It has some information about general operation of MoI and the section for Drawing / Picking points covers some of this stuff with some other information mentioned there too like how construction lines work.

Also in addition to that check out the video tutorials here which can also be a good help for getting started:
http://moi3d.com/2.0/docs/tutorials.htm

- Michael