This is what I did (on Windows 10 Pro - but will work on any Windows OS variant)
Download the zip folder.
Create a folder in C: root called MapViewer (Windows 8 and onward you will need to confirm this action as it requires admin rights to create a folder in the root of C).
Extract the zip folder contents to the folder you just created (C:\MapViewer). The folder should now contain two jar files. (mapviewer-0.0.1.jar and pngj-2.1.1.jar). You must move the jar files into the MapViewer folder.
Press Windows Key and R to to open up Run Dialogue, type in cmd press enter (this will open up a console screen).
Type in CD\MapViewer and press enter (you'll be typing this in after your username (e.g. c:\users\username> )
type (or copy and paste) java -cp .;./* ch.sfu.mapviewer.MapViewer and press enter ( you should be in c:\MapViewer\ when you do this on the console).
Program will launch.
Map files are located in: C:\Program Files(x86)\Steam\Steam apps\common\rising world\maps (not on my PC so this is a guess of the path)
(Should be enough information but if you need more just ask!)
Look closely at this screen grab:
