How do I drive more than two speakers with one... (by 7 users)

One amp can drive many speakers. However, there are two limits to this practice. The first is that you can overheat or damage an amplifier if you drive too low of an impedance to loud listening levels. Avoid loading any amplifier with a lower impedance than recommended. Adding two speakers to one amp output loads that output with half the impedance of one speaker.
The second is that with tube amplifiers, which are uncommon in today's common system, it is important that the speaker impedance and the amplifier output impedance be well matched.
When driving two or more speakers from one amp output, always wire them in parallel, rather than series. Series connection, while safe in terms of impedance levels, can hurt sound quality by raising the impedance that the speakers themselves see. Also, when different speakers are wired in series, amplifier voltage will divide between the speakers unevenly, because different speakers have different impedance-versus-frequency characteristics.
Many amplifiers have connectors for two pairs of speakers. In general, these amplifiers also have a speaker selector switch. Most amplifiers connect speakers in parallel when both are selected, although some less expensive ones will wire the speakers in series. It is common for these amplifiers to require 8 ohm speakers only, because the amplifier is built to drive either 4 or 8 ohms, and two sets of 8 ohm speakers in parallel loads the amplifier like one set of 4 ohm speakers. It is almost always safe to connect one set of 4 ohm speakers to an amplifier with two sets of outputs, provided that you NEVER use the second terminals for any other speakers.