The video shows the steps we take after a clean install.
You can type every command or you can put them in a text file and run that one script. The latter is more convenient.
I have a personal github to install elements after every clean install at github.
Here is the content of the script on January 2021.
sudo pacman -S --noconfirm --needed linux-lts sudo pacman -S --noconfirm --needed linux-lts-headers sudo pacman -S --noconfirm --needed optimus-manager-qt yay -S nvidia-390xx-dkms yay -S nvidia-390xx-settings yay -S nvidia-390xx-utils
After installing all the software and making all the smart choices you reboot, activate optimus-manager and select nvidia.