Joining galvanized iron fittings to galvanized steel pipe requires pipe dope or PTFE tape and two pipe wrenches. Start by liberally coating the threads of the pipe with pipe dope or wrapping the threads with PTFE tape. Make sure the pipe joint compound or tape go into the threads, to ensure a water tight connection.
Galvanized steel pipe was the mainstay for residential plumbing for decades. Copper pipe was available alongside galvanized but it was more expensive and used primarily on higher end projects. Copper is still used, and now plastic pipe is much more common, but galvanized is not used as much anymore. A lot of the fittings you see in the hardware store are used for repairs more than new projects.
