How to use the Min aggregate function along with group by clause in OTBI analysis

Summary:

I have a requirement to build analysis to fetch all the benefit enrollment data for a participant as well as dependent. I need to fetch the actual enrollment date of a participant & dependent into a plan type. When the employee moves from one plan to the other plans with in the same benefit Plan type (Ex Medical plan) the original enrollment date is updating with the enrollment date of new plan.

Ex: We have 4 medical plans with in the benefit Plan type 'Medical' i.e Medical TP1, Medical TP2, Medical TP3 etc. An employee can switch from TP1 to TP2 any time, I need to report the date when the employee actually started his coverage in the Plan type 'Medical'.