Help with joining two fact tables

Hi,

I'm relatively new to Power Bi and have created several reports and dashboards. I want to extend one of my reports, which involves adding in another fact table.

Table One has details about student risk assessments: dates, status etc. Any one of the dates could be null.

(Student_ID, date last updated, date of the last summary, date of last sign off, status)

Table two has details about staff viewing the risk assessments

(Student_ID, Staff_ID, Date viewed)

I have a calendar table.

I already had a matrix visual showing the information based on table one and I want to add a new visual that when the user clicks on a student from the other visual, it shows which staff have viewed the risk assessment since the last update.

I'm not sure the best way about approaching this, so any help/guidance will be much appreciated.

Thanks

Stuart