Adding repository in ubuntu

In order to download and install a particular software from a given url in ubuntu after recognizing it as a repository so tools such as synaptic package manager can automatically download and install the packages,you need to add the given url as a repository for that

Type sudo gedit /etc/apt/sources.list in terninal

paste the sources or url's to sources.list file and save

Then you may reload your synaptic package manager,you will then be in a position to install packages from the url