If you have a Zone VI film washer for 4x5 the 2 7x27 are used to raise it off of the bottom. You took out enough dividers in the center so the film washer fit in, Putting the 2 short sheets in raised the washer enough that you didn't have to lower the sheet film through a foot of water.
The orientation of the tabbed dividers is correct and you are just missing the cover piece, which was to hold down floating paper. I am sure the original owner lost it long ago. I have never needed it with my 11x14 washer to keep paper from floating and only use it as a cover to keep out the dust.
As for instructions, add hook up water and you are about there.