You can create and set tags in the “Resource Tags” tab which is located under “Settings”. You can choose whether to allow users to create tags on the fly from your settings menu. Otherwise you can define the tags that are available to choose from.
Go to your Settings in the top right header
In the left side bar, select Tags
Choose between Resource or Projects Tags and then type to enter a Tag. Press , or enter to add a new tag if this option is available from the “Settings”