When you cycle over to the Ships part of the menu screen, you will notice that there are quite a few different ships that you can unlock. One of which is the Steadfast (Capital Ship)
The Steadfast, despite not being flyable, turns up as a random encounter in planets such as Exegol and Jakku. Simply head into space and fly around and it should appear in one the two locations.
Head to either Exegol or Jakku space and fly around until you encounter the Steadfast. Once it appears, make your way towards it.
We will then be tasked with seizing the Steadfast, simply destroy the ship’s defences. This will include TIE Fighters and turrets.
Once the defences have been neutralized you can board and attempt to takeover the Steadfast. This will result in having to find and defeat Captain Swarton.
After successfully defeating Captain Swarton the mission will be complete and you can then purchase the Steadfast for 3,000,000 Shiny Studs