This is a how-to get set up and use MultiMC, which is an alternative to the Curse/Twitch/FTB launchers.
Get it here: https://multimc.org/
Get All The Mods 3 - Remix 1.6.0 here: https://www.curseforge.com/minecraft/modpacks/all-the-mods-3-remix/files/2990415
Unzip/install MultiMC and open it. Select your language:
Choose a java version, typically the default is fine. Be sure to change your maximum memory allocation! I set this to 12GB on my machine, you want to give it at least 4-6GB for best performance
Enable or Disable analytics. This allows the developer of MultiMC to see how many people use their application. You can read about it at the link included, or just disable it.
Choose "Add Instance" in the top left corner
Select "Import from ZIP"
Select "Browse" to find the zip file you downloaded from curseforge
Select the file and click "Open"
It may take some time, depending on the speed of your internet connection, be patient and wait for it to download the modpack
Once it is finished, you will see the modpack displayed on the main MultiMC screen! Click Launch!
If you've never run MultiMC before, it will prompt you to add a Mojang account. This step is required for you to log into Minecraft and join the server
Clicking yes will bring you to the account screen ,where you can click "Add" to add an existing Mojang account
Once your account has been added, click "Close"
Once you click "Launch" again, it may take some time to download the official minecraft binaries from Mojang, and then the game should launch!