Put Portalmapeditor.vpk in addons folder.
Put the other files in SAVE.
Note: If the addons folder doesn't exist, create one.
In the console write, load quick

File Name: Map.rar
File Size: 959.23 KiB
Click here to download Simple Map

In case it wasn't clear enough, this is one of those first person editors played from within the game. To be classified as "other files".

Please read the tutorials thoroughly before posting anything.

Actually there is a map to play if you load the included quick save, which is not half bad in terms of concept. However there does not seem to be an end/goal to it (though there is a clear progression), or have I missed something? I got up to the sequence of 4 faith plates that bring you back a place where you've already been before., I've been everywhere on the map and there does not seem to be any exit or end room.