That is not what I am referring to look at the bottom FOR VBULLETIN 4 ONLY. The stuff your talking about is the last step of install where you set paths and turn on the vbulletin header you already did that. You need to properly install plugins. I would assume if your getting errors on plugins you did not install them correctly which is why I am referring you to the install documentations to read the plugin instructions.
PhotoPost PHP Photo Sharing Photo Gallery Installation Guide
Feel free to post a url to your gallery install if you want us to make comments based in fact.