Open Cydia. On the bottom "dock", the 4th option over is Manage. Select that, and then select Packages. This is a list of the Cydia apps you have installed. Simply select the app you wish to remove, then in the upper right hand side select Modify, and then select Remove.
You might want to know this too. If you downloaded something that required 2 or more things to downloaded for it to run, you might want to delete those as well. Also deleted some things in Cydia doesn't mean it's complete off your iPhone. You can delete something and parts of the downloaded can still be found in your phone when you look for it via iFile or SSH. Hence why some people ask why they have so much junk taking up space in they're HD when they check on they're iTunes. Just a heads up. That's why when I download something from Cydia, I always check the "Confirmation" page and see what else is being downloaded besides the main name of the package. If there is more than 1 thing being downloaded, I take a screenshot and when I decide to delete it, I check the pic and see what other things I have to deletes besides the main package.