You question is only set up reminder date or reminder notification ?
I assume that your expecting to set up the reminder date.
For this, you can configure Info type 0019 (monitoring task). with the help of dynamic action. you can set up the condition for reminder date in IT0019 based on date of join.+2 month
You can use below
P0019-VTRAN=2
P0019-VTRZH=012 (this indicate months)
P0019-VTROP=+ (this will add 2 months from the date of join ((P0000_BEGDA)