how do you add a new partner to a 1065 return

[Just-Lisa-Now-]

From the K-1 worksheet, hit Page Down or the Enter button over and over until it moves down to the next partner entry screen.

[taxiowa]

What Lisa described will work if you are just adding a partner.  Although getting the mechanics and % to work out is still not easy. 

However that method will not work if replacing a partner.