You still need to add this to a shipyard, but I cannot remember how you do this, so someone else will have to help you there. Using search or selecting class/race (etc.) you can find any needed space ship. Here you can find technical data and specifications of space ships, compatible weapons, external view (screenshots of all ships). When you are finished you can save the file again and x3ed2 will automatically place it back in the cat/dats set for you. This part contains full reference information about space ships of the game 'X3 Terran Conflict'. There are multiple tabs there, and as you haven't done this before I suggest you have a look at all of your options before you choose what to change. Now you can click on your entry at the bottom of the left-hand list, and then change the values as you wish in the tables on the right hand side. This is important, if you paste into the list where you are you will corrupt the indexing and that will cause weird things to happen in the game. You will get a box pop up, in this box you must choose "paste at end". Once Tships is open, find the entry for the ship you wish to use as your base in the left hand list, then right click it and choose duplicate (or something similar, I haven't got the program open in front of me atm, but what ever the option is called it should be obvious which one it is.).
That way when you find the file you know it is the latest version the game is using and not a version in a lower numbered cat/dat set that will be over-ridden by an updated version of the file in a higher numbered set. X3 cat/dat sets over-ride the lower numbered ones, which is why you start from the highest number and work backwards. If you cannot find it, then open the next cat/dat set down and look there instead.
Use x3ed2 to open the highest number cat/dat set in your installation folder, and look for a file called Tships. You already have X3ed2, so no need to get that again.
#X3 terran conflict ships mod#
The biggest and main mod site is actually the Egosoft scripting and modding forums: