You can install pak via cargo using the following command:
cargo install pakcli
If you want to install pak manually you can go to the main page, and download the latest version. This will download a pkg installer which can then be ran to install pak.
If you use homebrew you can install pak using the following commands:
brew tap Interfiber/homebrew-tap
brew install --cask pak
The installers are NOT codesigned, which means macOS will not open it. To open it RIGHT CLICK the file in finder and click open.