@williamatics They’re just details, don’t waste your time with Booleans. You can learn how to use them later. For now, just stick them together.
If you insist on the bevel, maybe this will work (sorry for the many screenshots…):
I used a Cylinder for this example and divided it, so that I had more or less squares:

Select what you want:

Inset:

Extrude a bit and the extrude again:

Flatten the top (S, Z, 0 with Transform orientation changed from Global to Normal!):

An edge loop at the top and another inset:

A Subsurf Modifier and Smooth Shading gives this:

See if you can use this in your case.