No you’ve done all the hard work- Your models and thumbnails are now in the game folder. Lets get down into getting them into the game.
Click back until you get to the Galciv2 root directory C:\Program Files\Stardock\TotalGaming\Galciv2- Open the data file, and find the Shipcfg folder
Open it- your address bar should look like this:
C:\Program Files\Stardock\TotalGaming\GalCiv2\Data\ShipCfg
Once that is open, I would recommend minimizing the window and heading back to the Galciv2 folder using another window-
C:\Program Files\Stardock\TotalGaming\Galciv2\Gfx\Models folder.
To make this A LOT easier, goto your browsers Tools – Select Details, and then tell it to arrange icons by > Type

Tap back to your other open Browser window (C:\Program files\Stardock\TotalGaming\GalCiv2\Data\ShipCfg)
In this example we are going to change the human designs. If you want to change another design here is the key: s0_ Human, s1_ Torian, s2_ Yor, s3_ Dregin, s4_ Altarian, s5_ Dread Lords
Important to note- the humans are s0 as in s-zero, not s-Ohio- Common error to watch for. Here are the files we are going to change *Only .shipcfg files I know of that well get ships into the game
S0_ColonyShip.shipcfg (hull type: Cargo)
S0_CombatTransport.shipcfg (hull type: Huge)
S0_Constructor.shipcfg (hull type: Cargo)
S0_Defender.shipcfg (hull type: Small)
S0_Freighter.shipcfg (hull type: Cargo)
S0_Scout.shipcfg (hull type: Tiny)
S0_SurveyShip.shipcfg (hull type: Medium)
S0_Transport (hull type: Cargo)
In this Example, we will change the ship for the Transport- so find the S0_Transport.shipcfg, right click on it and select Notepad++, if you didn’t download Notepad++, you can simply open it with Notepad.

Now, that we are in the file, I normally highlight and delete all everything below BASE_HULL

Which leaves us with this:

Now, I go find the ship I want to use over in the second window (C:\Program Files\Stardock\TotalGaming\Galciv2\Gfx\Models folder)
In this case, it’s a Borq ship

Then I simply replace the S0_Cargo_0 with S99_BorgCube
IMPORTANT REMEMBER TO LEAVE THE .X EXTENSTION