http://www.moddb.com/games/ashes-of-the-singularity/tutorials/ashes-of-the-singularity-modding-guide

Basically, you already have it... just have to enable it.

To enable the Map Editor add the “-modding” (without the quotes) to the Launch Options for the game. That will add a Map Editor button to the main menu of the game. From there you can decide if you want to modify an existing map, or create a new one. If you create a new one the menu to the right is presented. For your first map I’d select a smaller map size. You probably assume that you will run out of space quickly on small maps, you would be wrong. Ashes small maps are what other games would call huge. The large ones are ridiculous and will take a lot of time to design. Practice on some small ones first. I selected Terran (grassland) terrain and default lighting. As you will see in the demo I change to Frozen terrain later, it’s easy to do so don’t worry too much about your selection here. The following is the default map that you are given. It starts with 2 player Nexas’s (Nexi?), a Turinium Generator and one other region. But we have lots of things we can add.

Dunno why that info isn't here.

It also looks like you need some extreme RAM requirements, we are talking 32GB of RAM!

I'm currently building a box with 64GB so I can do bigger maps myself.

Another fun mod thing I like to do:

Go into the \lighting directory and you can copy/past one of the lighting CSVs and mess with it and then iinside your map directory mess with the graphicssettings.csv to use your lighting file. 

Make sure you add trees (see other maps) or else it'll be barren.

The Map Editor is not for everyone, you really need a very powerful computer with a lot of Ram to handle the maps.

so i do recommend a minimum of 32GB of ram and a great video card.

But the Dev's need to start Optimizing the map editor to make it better, with more options and faster.