Tekxit 3.14 is nearing it's release, go play that instead, it's better in every way at this point :P
Installing a modpack using the Technic Launcher is easy. If you don't already have the launcher downloaded, visit our download page to get the latest version.
Type in the modpack name (Tekxit 3 Old (Official)) or paste the following url into the search box.
Finally, click Install at the bottom right of the launcher after you select Tekxit 3 Old (Official) from the list on the left. The launcher will handle everything else!