These are the only options you need to concern yourself with:

1. The main (diffuse) texture. Just replace the image here with the texture you want to use.

2. The displacement texture or heightmap: also replace the image inside this group with your own displacement texture.

3. Depth: this is the strength of the effect. Larger values will increase the depth of the parallax.

4. Non-planar: check this option if you're geometry is anything other than a plane (e.g. a sphere, cylinder, etc). Just be aware that some warping might happen.

5. Use these to scale your texture in the X,Y or Z axis the same way you would scale it using a mapping node.

6. Specify your light object here for self-shadowing.

7. If you don't want self-shadowing, cut these connections.