To install Fatdog64 pet packages you can use the link on the home page to the Fatdog64 pet package repository. Then just download the package you want and then click on it. Do not try to install the pet package without downloading it first, the web browser (Firefox/Seamonkey) doesn't have permission to do that (as explained in browser security.
Or you can use the Fatdog64 Package Manager. It can be found under System from the Control Panel. Use Space bar or Enter key or double-click to mark which packages you want, thenn click "Install" button to install them. If the package you want is not shown, try clicking Refresh - this will re-download the package list. You can also un-install packages using the Package Manager. Some packages needs other packages before they can work - this is called "dependency". You can enable or disable dependency checking.