Start with a PTP 820G link.
Change the link to 1+1 Hot Standby, since PTP 820G's space diversity is built upon 1+1 Hot Standby.
Notice under "Antenna Configuration :", there is a "Spatial Diversity" option. Select it on both ends of the link.
Be sure to space the antennas the recommended 200λ distance for space diversity. (For example, this is roughly 30 ft for 6 GHz and 20 ft for 11 GHz.)
Done!
Oh. Wait.
If you're planning PTP 820i, there are two space diversity options!
Ha!
One is "Spatial Diversity (Split End)" and the other is "Spatial Diversity (Standard)".
See the PTP 820G documentation or the forum for the differences between these two options.
I hope this helps!
Dave