GT New Horizons updated to version 2.3.1
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 (GT New Horizons) or paste the following url into the search box.
Finally, click Install at the bottom right of the launcher after you select GT New Horizons from the list on the left. The launcher will handle everything else!