The Arch User Repository is one of the jewels of the Arch Linux distribution in my opinion. The catch is that it CAN be difficult to install packages from it without a helper. And the helpers are in the AUR, leaving us with a chicken and egg situation. Here’s my recommendation on how to install apacman.
Go to the github repo for apacman. In the right column near the bottom you’ll see a small form with the clone URL:
Make sure you choose HTTPS, unless you already have ssh keys set up.
Copy the https url and then open up a terminal on your local machine. Run this command:
git clone https://github.com/oshazard/apacman.git
That will download all the proper files and put them into a directory called apacman. Cd into that directory and run this command:
./apacman -S apacman
and follow the instructions. When it’s done apacman will have been installed from the AUR. Then you can cd back up a directory and remove this local apacman directory with
rm -R apacman
At this point you can now run apacman from anywhere.