1) You need money. Lots and lots of it (figure at least 1mil).
2) Find a seller. Look through the Commerce forum, Auction Hut. You can look at the ship factions and see which one is selling what you want. You can also look at the centerpoint market which is an off-site market website. Access it through the Centerpoint Spacestation faction link.
3) Arrange the deal. Best thing to do is use a middle as this prevents you from being scammed and them stealing all your money.