Here's a quick GIF to make the process as easy as it can be.
Labels can be applied to issues and pull requests to signify priority, category, or any other information that you find useful.
On GitHub, navigate to the main page of the repository.
Under your repository name, click Issues or Pull requests.
Issues Labels buttonNext to the search field, click Labels.
Click New Label to create a new label, or click Edit to edit an existing one.
In the text box, type your new label name.
Select a color for the label from the color bar. You can customize this color by editing the hexadecimal number above the color bar.
I hope it helps. Upvote it if it does.