You have four options to add Tags to your candidates:

1) You can do it directly in the candidate profile - just go to Tags section, visible under the candidate avatar. You can choose one or more tags for each candidate.

2. You can also do it on the candidates list (talent pool or in a particular job). Choose 3 dots at the end of the line to select a single candidate or put a tick next to multiple ones and choose Add tags and talents option. A new window will pop up where you can add tags as explained above.

3.  Visit the quick preview of a candidate in a job - you will see the option to add tags on the right side of the CV preview:

4. Add tags when creating a new candidate profile manually:

NOTE: Adding new tags (not available one the list) can be disabled for particular permission groups by the administrator.