You will receive instructions with your order. They recommend either brads (which I used) or glue which is temporarily aided by brads that are pulled after the glue dries. My Homabed was installed over Homasote which serves as the base for yards and sidings. Because I have used Walthers/Shinohara track that takes spikes, I wanted a roadbed that takes spikes readily.

If you are spiking into the Homabed, you will have problems driving the spikes into the plywood subroadbed below. That is another reason I used sheet Homasote screwed as a subroadbed over the plywood.

To answer your question about glue, I have tried to avoid glue anywhere in the benchwork, subroadbed, roadbed and track construction so that the layout can be more easily disassembled and salvaged when the day comes that I go!  

All that being said, there are a few spots where I had to use glue to secure the feather edges of tapered Homabed and make a few other small repairs:  I used undiluted white Elmers glue.

Dante

I used both white glue and yellow carpenters glue to laminate homosote to plywood. The yellow carpenters glue will be stronger and repel water compared to the white glue. I liked the yellow glue better.

I applied an even layer of glue to both surfaces then weighted the sections overnight. I coated both surfaces because the homosote sucks up the glue really quickly. You might choose not to do this on the homosote to plywood, but I would certainly coat both surfaces when gluing homosote to homosote.

White glue.  Buy the gallon jug.