Hi Silver, a good place to start is the help file here:
http://moi3d.com/2.0/docs/moi_help.htm

Read the introduction section which is here:
http://moi3d.com/2.0/docs/moi_introduction.htm

And then watch the video tutorials here:
http://moi3d.com/2.0/docs/tutorials.htm

Watch those a couple of times and then also try following along with them to construct the same object yourself. That should give you a good overview on the overall construction process.

Then it's not a bad idea to read over some of the command reference part so you can get a better idea of what each particular command is for, that's available here:
http://moi3d.com/2.0/docs/moi_command_reference.htm


There are also other videos collected here:
http://moi3d.com/resources#Tutorials

One of the best of those for beginners are the ones by Tom Meeks that Brian has a link to above.

Hope this helps get you started!

- Michael