There are 2 ways to do this, Post Process and Dynamic.
From the Route Menu > Teardrops and Breakout Traces..., Select Dynamic Teardrops to add Teardrops as you Route your design.
Second, if the board is already designed, you can Post Process teardrops by selecting the same menu, and using the setup dialog as shown. I have found that the Ratio settings of 1:1 work well for most designs. There is help available for this dialog.
and how to set in Mentor BoardStation RE, looking forward to your reply