This blog post shows you how to create an annotated tag in git; using github. I assume you already have git installed and have at least a working knowledge of the basis.
Create the tag
git tag -a v1.0.0 -m 'some message'
This is how you push tags to the server (regular push does not move over tags)
git push --tag
To view all tags:
git tag -v
To delete a tag (use the view option above to get the tag name )
git tag -d v1.0.0