Hi LordSethD,
The easiest way to learn how to do this would be to look at the data files for the existing races. Have a look at the PlayerPsi.entity file.
If you make a copy of this file called PlayerX.entity and edit it, you
should be able to see it in game. The "raceNameStringID " at the top
is the name of the string (in the English.str file) which has the name
of that particular race, so you'd need to add a new string to the
strings file with your race name.
At the top there are lists of all the orbital modules and ships that the player can build, then all their research subjects, and a bunch of customization data. If you want to change the ships from the standard Psi (Advent) ships, you'd replace CAPITALSHIP_PSIBATTLESHIP with the name of one of the ships you've added.
Keep in mind that when you modify groups of something there will often be a "count" variable which tells the game how many of that item to look for, ie:
aiNameData
nameCount 10
name "IDSPlayerAINamePsi0"
name "IDSPlayerAINamePsi1"
name "IDSPlayerAINamePsi2"
name "IDSPlayerAINamePsi3"
name "IDSPlayerAINamePsi4"
name "IDSPlayerAINamePsi5"
name "IDSPlayerAINamePsi6"
name "IDSPlayerAINamePsi7"
name "IDSPlayerAINamePsi8"
name "IDSPlayerAINamePsi9"
If you add another aiName, you HAVE to make sure that the count gets updated, otherwise the game will crash when it loads.
Hope that helps!