Mandatory training is training your organisation has assigned to you for compliance. It has to be completed, and often by a due date.
Where to find it
In My Learning, a notice at the top reads You have mandatory training to complete, with the line "Complete them to stay compliant and keep your learning on track." Click View and complete to see it, then Continue to open the item you have already started.
Under Activities › To Do you will find everything assigned to you, mandatory or not.
Under Shares › Received is what colleagues or managers sent you directly.
How it is completed
It depends on the content. Watching a video to the end and setting Mark as to Completed may be enough. If the content has a quiz, it only counts as completed once you have passed it — and that is also when you receive the certificate.
Good to know
The date you completed it is recorded, along with your quiz score. That record is what your organisation uses to demonstrate compliance, so it is worth not leaving it to the last day.