Hi Rachel, welcome to MoI!

To place a point at a specific x,y,z location you just type those in directly when MoI is asking you for a point. So for example if you want to place a point at x = 40, y = 30, z = 5 you would type in:    40,30,5    and then push Enter and the point will be placed at that location.

Note that if you are in a location that uses the comma as the decimal point for individual numbers (like France for example where the fraction 1/2 in decimal is shown as 0,5 with a comma as the decimal point separator), you should put a space in between the coordinates rather than a comma.

If you are using 2D x,y coordinates where z = 0 you can just leave out the 3rd coordinate and only enter in the x,y . You can also enter in a single 0 as a shortcut for 0,0,0 and there are also some other coordinate entry methods like polar coordinate entry where you can enter in a distance and angle from the previous point rather than x,y,z coordinates. The different types of coordinate entry types are listed in the help file here:
http://moi3d.com/2.0/docs/moi_command_reference1.htm#__XYZ%20/%20Distance%20/%20Angle

When you start typing your coordinates the characters you type will go into the x,y,z coordinate input box which is on the bottom toolbar next to the Split/3D/Top/Front/Right view tabs:


So watch there as you type in your coordinates, you will see your text in that location when you start typing, then push Enter when you have finished typing the coordinates.


> In the 3D view I can't really understand how the cursor moves around, but it always seems that
> when I place it where I want my selection point, the point ends up either far in front or far behind
> (in the direction perpendicular to the computer screen)

It works by intersecting a screen ray with the construction plane - the screen ray is a line that goes from the 3D view's eye point out through the current mouse location - if you are looking at the construction plane at some kind of angle the intersection can possibly be a long ways off - it can be easier to draw points on the plane in the Top view instead of the 3D view, or at least angle the 3D view so that you are looking to some degree more downward at the plane rather than looking more towards the edge of the grid.


> the plane it moves on is (as far as I can tell) immutable.

You can actually relocate the construction plane somewhere else by using the View > CPlane command. But that's fairly advanced and I'd recommend just practicing drawing on the default construction plane for a while first, and maybe some more strategic use of the Top view rather than the 3D view would also make things easier as well. The Top view is fundamentally a 2D type view, with no perspective distortion on it or anything like that at all so it tends to be an easy place to draw 2D type stuff in.

Hope this helps, let me know if you are still stuck on anything in particular.

- Michael