it clearly says how to install it ??
• Installation
- Copy the latexreference folder to the products folder at the root of your vBulletin installation. NOTE: If the products folder doesn't exist you must create it.
- In the latexreference folder, under the includes/xml folder there are two xml files. Copy these two xml files to the includes/xml folder in your vBulletin installation.
- From the vBulletin control panel, on the left navigation menu, expand the "Plugins & Products" menu and click "Manage Products".
- In the "Installed Products" screen click "Add/Import Product".
- In the "Import Product" screen do not specify a file to upload. Instead import the product from the xml file you copied earlier to the vBulletin /includes/xml folder. The path to that xml file is: ./includes/xml/product-latex_reference.xml
- Click "Import". The Latex Reference product is installed and configured.