OpenIndiana uses the same package management system as Oracle Solaris 11, and Oracle is thus far continuing Sun's practice of providing well written manuals:
The command line package manager is 'pkg'
Set a remote repository:
sudo pfexec pkg set-publisher -O http://pkg.openindiana.org/dev openindiana.org
Search for a package:
pkg search -pr git
Install a package:
sudo pkg install git