Load any photo.
Select the brush tool
Click "Windows" at the top of the screen.
..click brushes
In the brushes pop-up:
Click brush presets
At the top of the pop-up window, click the black triangle to the right of the "brushes" tab.
In that pop-up window click "load brushes"
Select the brush set (.abr file) you want to add.
Click Load
Scroll down the brush shapes window and your newly added brushes will be at the bottom of the list of brushes.

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