Making holes and centering items correctly

HudsonRed

Hey everyone. New to 3D modelling but need it since 3D printing is the best option for my next project.
So I have two problems. The first one is I want to make that red rectangle and pink circle hollow (a hole) and I also want to center everything in the middle of the main circle (largest one).

I have attached the file so Im hoping you guys could help me out.

- Red

Krato

I'm not familiar with whatever program you're using, but one approach is to set the objects origin to the grid center (where x and y meet), and then to center the object over to that origin. 

If it's like Blender
1. Set object's origin to grid center
2. set object to move to origin
3. Transpose/move object in grid snapping until satisfied if needed. 

Or if it's like Maya
1. Go into edit mode
2. Select a vertices (one in the bottom center of the circle where all the edges meet), and make it the object origin
3. move the object, snapping along the grid plane, to the center of the grid, until your origin is centered on the grid.

I don't recognize what program that is, is it modo? Whatever it is you could probably google something along the lines of "center object on grid in X program" or watch basic tutorials.