Then plug the PC in, plug in and connect your monitor (to one of the ports on the graphics card, if you've installed on) and your keyboard and mouse.
Once all that's done, it's a good idea to double check to make sure there are no extra fan headers or power cables still waiting to be routed to the right connector. Then plug the PC in, plug in and connect your monitor (to one of the ports on the graphics card, if you've installed on) and your keyboard and mouse.