Yellowfin automatically tracks user activity and stores this information in the Yellowfin DB under the 'Event' & 'EventArchive' tables.

A list of all info logged can be found here :
Report Auditing and Tracking

In order to create reports to return such informaiton, you need to make sure you have a data source connection to the Yellowfin DB.
Once you have this connection, it's just a matter of creating your view that includes the event & event archive tables.

During installation there is an option to install Usage Reports, which contains reports/dashboards/views for auditing purposes, however if you did not choose this, you can downlaod an export that contains this view & reports by right-clicking here and choosing 'save-as'

Please note this export comes from Yellowfin 6.3 and DOES NOT include the data source connection, you will need to make your data source connection, and then simply import the views/reports/dashboards.

Not sure how to make a connection to your DB?
Check your Yellowfin DB connection settings listed in the web.xml as mentioned here: Connecting to the Yellowfin Repository DB

If you're using HSQL, then your connection details may not be famaliar, so the following posts should help :
-Install Usage reports
-Using Linux - What is HSQL URL string format

Regards,
Yellowfin Support