Correct, find and insert you bump image there. Just experiment; if you set the multiplier higher you get more bump, if you insert a power fractal in the function input, the bump is affected by image as well as PF. Offset makes the bump raise/lower from you offset, which I never use, by the way.
But you can also add a no color PF between the parts shader and the default, with displacement. That adds bump as well.
By the way: I did some simple tree fungus. Same seed and X/Z-rotation offset (in objects) and they stick to the trees.