curl -fsSL https://www.pxb.app/cli/install.sh | sh

That drops a single executable into ~/.local/bin/pxb. If that directory is not on your PATH, the installer prints the line to add.

Install somewhere else:

curl -fsSL https://www.pxb.app/cli/install.sh | PXB_INSTALL_DIR=~/bin sh

Piping a script into a shell is worth being careful about. To read it first:

curl -fsSL https://www.pxb.app/cli/install.sh -o install.sh
less install.sh
sh install.sh

Re-run the installer to upgrade. To remove it, rm $(command -v pxb) — run pxb logout first if you also want its keychain entries gone.