Simple: you're going to need to use the Credits currency. Before you pick up more of these over time you'll have to head over to the cash-shop to get hold of some more. Prices vary across regions so check from your device.
Star Citizen is an upcoming space trading and combat simulator video game for Microsoft Windows. Star Citizen will consist of two main components: first person space combat and trading in a massively multiplayer persistent universe and customizable private servers (known as Star Citizen), and a branching single-player game (known as Squadron 42). The game will also feature VR support.
