This tutorial assumes that you have read installing steam arma 3 tools page and the tools are installed. You could setup P: drive or workspace as bis calls it, without the tools put there is not much point doing that.
Setup P: Drive
You need to create batch file to subst P: drive. You can place this bat file any normal directory you want, do NOT drag it into windows desktop, its not a proper place. What is a proper location then, well for example c:\arma3work\ directory is good, but choose any drive/dir you want.
Make sure the filename extension is “mapdisk.bat” instead of “mapdisk.bat.txt” which could happen if you have windows explorer “hide known file extensions” turned on, you need to turn it off.
Use this for “mapdisk.bat”:
subst p: /d subst p: "c:\arma3work"
Replace “c:\arma3work” directory to where you want to keep your work drive. Do not use ArmA 3 Tools directory. You obviously have to create this directory. Next just double click mapdisk.bat to activate the new P: drive.
You might want to setup mapdisk.bat into your windows startup programs so you don't have to click it every time you restart your computer and want to edit ArmA 3.
Download ALL the Latest Versions of the required Mikero tools. You should install them all, but you must install these bare essentials:
After you have activated the new P: drive (by running mapdisk.bat), run Mikero's tools ArmA3P.cmd (a batch file, just different file extension) and wait… ArmA3P.cmd should run all the way - with no errors, and report success. This will take really long time, be patient and wait.
When this is done, your brand new P: drive is ready for some ArmA 3 Terrain Editing