Tags are basically keywords for each page/article/event you create.
Tags are intended to be words or very short two or three-word phrases. Adding tags that accurately represent a post or page will increase the chance that it will get its due website traffic. To add a new tag, follow this simple instruction.
Adding Tags in Modern Events Calendar
Enter your tag,
Enter your slug.
Note: Your theme must support the description field in order to show it.
The final results should look like this (if your theme supports WordPress tags):
Tag Methods
Also, you can separate the Default WordPress tag from MEC tags by navigating to MEC Settings > General > Advanced and changing the Tag Method to Independent Tags.