When your mechanic completes a task and marks it as "resolved" it's saved as a vehicle maintenance log.
To view the maintenance log, navigate to Fleet > Maintenance > Log.
To set up a Maintenance Admin, see this article.
Log unscheduled maintenance tasks:
In addition to checking the maintenance log, administrators and mechanics can create log entries for vehicles to log when unplanned service on a vehicle has been performed.
On the Maintenance Log, select + Create Log Entry.
Here you are able to enter in the necessary information for the Log Entry.
Be sure to press Save when you are done. If you do not immediately see the log entry after selecting Svae, please refresh your page.