When you are working with a brush in Photoshop, you
sometimes need to tilt, turn or flip it. Here's how:
In Photoshop, select Window > Brushes to activate the Brush Presets.
Choose “Brush tip shape.” You’ll see a feature that looks like a
compass. You can turn that to turn the brush. Just click/drag to
rotate it. You can also type in the new angle in the “angle” box to turn
the brush a set number of degrees. You can also turn 180 degrees to flip
it.
The brush presets box can also be activated by selecting the brush tool.
The brush presets icon looks like a square box on the right side of the Options
bar near the Bridge and Workspace icons.