Once you have downloaded the brush you want to use you should unzip it to your folder > Presets\Brushes
Open Photoshop
On the tool bar click on the brush icon
In the Tools Options bar, click the arrow next to the Brush pop up to display the pop up panel then click on the >> arrows to open the sub menu.
On the side menu click Preset Manager.
On the Preset Manager Menu click on Load button and browse for the brushes you want to install. Once you load the brushes click done.
Go back to the Tools Options bar, click the arrow next to the Brush pop up to display the pop up panel then click on the >> arrows to open the sub menu and click the save brushes on the bottom of the menu.
