How do I need to set up this program?

You may have to install MicroSoft's .NET Runtime Library, if you haven't installed it already. You can get this from the MicroSoft website.

Once you get the program up and running, you need to set your Steam folder location. When you set your Steam folder, it will automatically recognise which game(s) you have installed; the buttons and menus for the game it recognises are enabled.

What do I do when my game is in another location? 

If you have your games in another location than where Steam is installed, you can add that folder by adding a semicolon ; to the Steam folder line and after that the root folder of where the games are installed. If you do this correctly, the launcher will enable the games it can find at the defined location. Example:

Code:

C:\Program Files (x86)\Steam; D:\My Other Games Folder

So this program doesn't work for non-Steam versions of the game?

That's correct. It will also only work on Windows PCs.

Are the DLCs I have installed automatically recognised

No, they aren't. Due to inconsitencies in the naming of the DLC packages and their actual online name, I couldn't make an automatic recognition algorithm. You can edit the DLCs it can recognise yourself, however.

The lists below will give you an overview of the tags for all map DLCs

ETS2: Code:

 TAG     | NAME       
---------+------------
 east    | Going East     
 north   | Scandinavia    
 fr      | France
 it      | Italy     
 balt    | Baltics 
 balkane | Black Sea