Have you read this?
That tutorial is correct and works. Only thing is i personally find the Z is still off and i use a much lower value than they recommend. Anyhow, this should help you understand tiling in WM.
The res that they are using per tile will require a bit of experimentation as well, recommended landscape resolution sizes can be found here:
Again experimentation is key.
What i suggest you do is you break this process up into 2 parts when hunting out learning material.
Learn the program for the landscape (ie World Machine) using tutorials just about that.
Then learn how to use world comp in the engine just by using those referenced docs and practicing.
To see it in action in engine and working (that tends to be how i learn, backwards, lol). Download the ARK mod kit. And load up some of there levels and have a play, you should be able to figure out world comp easy enough from that…
Good luck!
Remember, patience, and experimentation. 