If you are using the GUI, you can right click on your local directory and choose repository explorer to see what the branches look like. Then, you will want to remove the files locally, and then next time you commit and push changes they will be gone. To do this you would right click on the files you want to remove and choose "remove." It may prompt you to confirm this "clean." Then, commit and push changes. When you finsih this, log into your repository (i.e, bitbucket.org, kiln) and confirm your changes.
If you want to do this through the command line, type:
hg -? in Windows to see list of commands. Or, type:
hg --help in Linux for the help list.