In GitHub, the notion of a release is tightly tied to Git tags. You can see the existing tags, if any, from the same menu where you change a branch, as shown in the following screenshot:
If you visit the Releases page and there is no tag created yet, you will be prompted to create one. Creating a release will automatically create a tag.
Let's click on the Create a new release button. The following page will appear:
You only need to fill in the name of the Tag version box; everything else is optional. If the tag name you provide ...