How to merge to stl files together to print as one

Hi I am new and in need of some help.

How do i attach 2 stl files together to print as one. i have added both to the plate and clicked assemble but the logo disappears.

You could try Thinkercad, you can import STL files there and merge them on the workspace.
I’ve edited and modified STL files there myself, and it works quite well.
The link: https://www.tinkercad.com/

Hopefully this will be a solution for you.

By default, both items will sit flush on the build plate. After you assemble it, go to the objects menu and select the one you want to move then use the move tool to position it where you want such as on top of the other object.

which two stls are you trying to «merge»?