Early on in your training you should have been taught that an assembly file *.sldasm without part files *.sldprt is useless.
An assembly file is simply list of hyperlinks to the referenced part files and a record of assembly constraints of how they fit together.
You must attach the part files.
Without seeing you files a couple of options
use multibody solids technique and assembly isn't a problem
turn on temporary axis - did you model the parts with symmetry about the origin?
How are the parts assembled in the real world - that should give some clues of how to assemble in the digital world.