Stupid Question - How to center objects on top of each other

This is going to seem like a stupid question I'm sure, but I've tried to watch videos and everything and just can't seem to find the answer to this. I'm trying to put together a model for a base plate for a camcorder to attach to a bracket that I already have. It will consist of 3 rectangles of decreasing size, with a threaded hole on the bottom and a stud on top.

I've mocked it up in Photoshop (because that I actually understand how to use), but I just can't get the blocks to anchor themselves to the center point of the shape below in fusion.

This is my first foray into 3d modelling, so be gentle. Was thinking of rounding the corners of the various bits as well. not sure how much work that would be to do.

Anyway, any help would be appreciated.

The simplest way is to model them in place.
Start with the main "box"
For the next "box", create a new sketch on the face of the first one, and draw a rectangle. Dimension the rectangle relative to the edges of the first "box". When centered, extrude it to the correct height.
Repeat.

To round the corners, use the Filet command from the Modify menu.

I think I MIGHT have been successfulish.

You can draw a diagonal on them and line up their midpoints

i thought you needed in machine alignment sugestion :) for cam modeling, well, is easy :)

there are tools that allow to draw a rectangle from it's center/gravity point, thus, with such a tool, you simply draw 3 rectangles, by always selecting the origin as the 1st point

you know what i mean ? i can share later a pick from solidworks, if you wish / kindly :)

5 year old post.. .
If he hasn't done it by now, I'd have sacked him.

I think it can be done.

I think you can do it. If you are stressed and tired, try coloring pictures to help you reduce the Coloring combo pressure to continue working.