This sounds like a telephone installation. If the service coming in from the provider is dsl it is just a matter of connecting to the correct pair. If you do not have something that shows which wires go to which jacks you are in for a lot of work.
In phone installs what is normally done is one pair of wires is run to the center 2 pins in each jack. Since phone lines only need 1 pair this will work.
If what you are installing is not something like DSL then it is much more complex. You may have to rip it all out and rewire it if it is a telephone installation.