In the Automation functionality, it is possible to create actions when a automation is triggered. This way, you can also make a record being added to a certain tag, or also remove a record from a tag.
In the next step, you select the Object for this record, followed by the specific Tag you want this record to be added to.
Click on Confirm and the action is now added to your automation.
Want to know more about the Automation functionality? Read this article: Automations
Looking for more in-depth knowledge about the Tags module, where you can manage re-usable segments of records? Read all about it in this article: Tags