They only have a GUI environment if you created your droplet with a distribution that supports it (i.e. a "desktop" distribution, which I do not see as one of the options for CentOS). If you did that, you would be able to access it through the console -- the "Access" icon on your droplet's page in the control panel -- or, probably requiring some extra work on your part, using VNC.

You're in luck! There's a tutorial on this very site that tells you how: https://www.digitalocean.com/community/articles/how-to-setup-vnc-for-ubuntu-12

However, you should know a couple things. First of all, having graphics on your server is just another potential attack vector for hackers. It's not a guaranteed future problem, but it's something you should try to avoid doing in a production environment.

Second of all, I know that the command line seems overwhelming and hard to learn. That's because, well, the command line actually IS overwhelming and hard to learn. But, once you've properly learned it, you're going to see why servers don't come with GUIs. Every time you learn something new about one of the core command line utilities (like sed or grep), you're learning a new power that you can use in system administration. When you're using personal servers, try and force yourself to use the commandline as much as possible when you're solving problems. Once you get your head around it, you'll be amazed how much you can get done.

--Matt