Here i'll show you how to download the TechnicLauncher (the launcher that you need to play on a Tekkit server)

Steps

1) -Open your web browser of choice, such as Chrome,Opera,safari... (I recommend Chrome)
2) -Write technicpack.net in the seach tool. Link----> http://www.technicpack.net /
3)-Theres a section that is written "Modpacks" click on that and there is a list of ModPacks. Click the one you want to download, it don't really matter which one you choose. Once you click on the one you wanted your going to be redirected on the Mod Pack page, on that page find the ''Download the Technic Launcher'' and download it.
4)-There's not setup just drag the laucher to your desktop and double click on it to open the launcher.
5)-Once the launcher is open, at the left of the launcher you'll see a Mod Pack list, choose which Modpack you want to play on such as Hexxit and click on the play button. ( It might take about 2-15 minutes to download the ModPack you choosed. Depends on your computer speed)
6)-When the Pack is completely downloaded your going to be able to play on multiplayer and offline. (Just like the original minecraft launcher)
*To play on Hexxit server you need to have the same ModPack as the server have.
Example: There's a server that has the Hexxit ModPack, you wont be able to play on that server if you have the Voltz Pack, otherwise if you try to join with the Voltz Modpack you are going to have an error. You need to have the Hexxit ModPack to play on a Hexxit server
**To change your Modpack, go back to the launcher. Same as Step 5 and choose the one required to play on the server you want.

I hope this tutorial was helpful
Thank you for reading and don't forget to give me a diamond! :D

Feel free to tell me what you think of my tutorial or what could be added or modified.