How to install a .gha, bowerbird more specifically

I just downloaded the most recent version of grasshopper and am trying to install bowerbird.  I downloaded a zip file which contains the .gha.  The instruction direct me to drag the .gha file into the grasshopper window, but when i try to do that it has a circle with a line going through it.  Not sure what I need to do to open this in the most recent form of grasshopper