You don't install a respritory. They are severs on the net you tell your package manager where to get programs and updates from. How you do it depends on the package manager on your system.
Open up the package manager ( if you have one ) and look there. Limpus Lite has a web site. You could look there for a "how-to". Every package manager is different. They are created by the developers who put the distro together.