IMPORT A PACK IN TWITCH - kreezxil/World-of-Dragons GitHub Wiki
Go to the Curseforge page for the pack. Since you are here we will assume you want World of Dragons
Therefore goto https://www.curseforge.com/minecraft/modpacks/world-of-dragons/files and download the version of the client you want.
Now open Twitch follow the attached pictures.
After you open the client zip that you downloaded and hit open Twitch will begin downloading and installing the mod pack.
NOTE
Installing a mod pack in Twitch this way carries with it the same burden that installing a mod pack in MultiMC carries and that is neither will auto-update for you. You will have to do this each time you want to update the pack.