Open the file /etc/pacman.conf with sublime text and add these lines to it
SigLevel = Required DatabaseOptional
Server = https://arcolinux.github.io/arcolinux_repo_3party/$arch
Then do an update
sudo pacman -Syyu
then you can install the packages that are in this 3party repo.
Mid July 2018 we have added discord and its libraries in there.
Installing discord now is available with
sudo pacman -S discord
With the use of pamac you can easily see what packages we currently have in this repo.