Keep in mind the date, sometimes a lot of things change since 2009. Here's one of my more concise explanations from years ago.

Also remember to uncheck the "Use Default Template" option if you don't want the normal militia to appear.

FYI I've used templates maybe once, so I can't tell you anything about them. What I usually do is edit each planet with groups. No matter what though you'll have to edit the map in notepad after you've done everything you can in Galaxy Forged to get them to appear on unowned planets, as in previous post. The only difference is if you're using a templates you'll search for the template name instead of the planet name.

No, you just put "RandomMilitia" into the owner line, and set the parameter to "Always". The name RandomMilitia is already known to the game, you don't need to make a new player. That's already defined for you else where.

Here's one of my maps with a ton of customized militia if you want a reference with groups (assuming you have Rebellion). I don't remember if I used templates or not, but you should get a group working before you try templates.

Well, that helped, although it turned out I had some empty lines in my galaxy file which neither the game nor galaxy forge likes.

You cannot add structures to uncolonized planets for some reason. If you're going to add structures, you need to make sure the planet is owned by the player who will be getting the structures. The easiest way to do this is right below the owner line in notepad, you should see something like "ColonizeChance". Set this to 1.0, and the militia or whoever will own the planet and the structures should spawn.