It's pretty easy, Papa.
1) Load a map you want to work with in GalaxyForge.
2) Find NewPlayer0-Home; this is your capital.
3) Right click that planet and select edit. A new window pops up.
4) The second section from the right is Group Manager. Click Add. A tab should appear named "Always", that is what you want.
5) In the next group over, find "Spawn these items for". Change it from "PlanetOwner" to "NewPlayer0".
6) Look around on the list to the far right, this includes the ships you want. For example, pick "Phase:Titan:Loyalist", and click the far right add. You do not want the cosmetic titans at the bottom.
7) Once done, click okay.
8) Save the map.
9) You're done. Go eat some Orange Chicken or something.
When you play this map next, you'll start with a Vasari loyalist titan, or whatever ships you selected to add. Can use this to get all the titans, even multiples of all. You can not, strangely, add the new capital ships, as they are no where to be found. The rest, however, is fair game. Don't worry about cap/fleet limits, they'll be spawned and you'll just start in the negative. In addition, by using commands in Dev.exe, you can level up your new titans to level 10 in literally a second to check out their abilities.
If you need a map to play with, Dirty has a map pack you can download (link below). You'll probably enjoy his maps anyway, so worth a download regardless.