My small GPG rookie guide, which I wrote as part of the CPM manual might also be useful here.
$ gpg --gen-key
Enter 1, 2048, 0, y
Enter data to create the key for.
$ gpg --armor --output harry_b@eml.cc.asc --export harry_b@eml.cc
$ gpg --import <FILENAME>
$ gpg --edit-key harry_b@eml.cc
Enter 'fpr'
$ gpg --edit-key harry_b@eml.cc
Enter 'sign'
$ gpg --verify linux-2.6.11.tar.gz.sign linux-2.6.11.tar.gz