There are two ways to create a tag
From command line
Github’s interface
Let’s see how it can be done
To create a tag on your current branch, run this:
git tag <tagname>
To describe your tag:
git tag <tagname> -a
This will create a local tag with the current state of the branch you are on. When pushing to your remote repo, tags are NOT included by default. You will need to explicitly say that you want to push your tags to your remote repo:
git push origin --tags
if you just want to push a single tag:
git push origin <tag>
Then it will be pushed to the Github using the above commands.
Refer: https://git-scm.com/docs/git-push
Creating tags using Github’s interface.
1. Click on release on your repository

2. Create a new release

3. Give your tag here
4. Then publish those release
Thus you can create a tag from the github interface.