While it isn't a required step, it is recommended to verify the image before trying to use the ISO file.

Use GnuPG and import the Arch Linux Developer Key with the following command.

gpg --keyserver-options auto-key-retrieve --verify archlinux-version-x86_64.iso.sig

Once completed, navigate to the directory where your ISO file and the signature file are located. You can then verify the signature with the following command.

gpg --keyserver-options auto-key-retrieve --verify archlinux-version-x86_64.iso.sig