First thing you want to do after installation is configure your dotfiles. If you don't have your own dotfiles yet, fork my repo and clone your fork.
Make sure to grep for maximbaz and set your own username.
Once done, run setup-* scripts to finalize the installation.
To use your own custom pacman repository (e.g. when using aurutils), you need to register your PGP key in pacman.
TLDR: pacman-key --recv-keys <keyid> && pacman-key --lsign-key <keyid>
For more details, consult Arch Wiki.