How to use zRam.

[Moltke]

And what are the benefits of using it?

zRAM is intended for using in those machines with 2gb or less of RAM, actually you'd get better results and/or see any performance improvement with 1gb of RAM. If you have more than 2gb of RAM it doesn't worth the time since you won't see much of a difference regarding performance, in fact, and according to what I've read,  you'd probably see a decrease of it.
Hope this helps!