How do you use multiple amplifiers?
The best way to wire multiple amps to a single power cable is to use a power distribution block. That allows you to use a single cable for most of the run, including the crucial portion that passes through the firewall and then to use shorter individual cables to actually connect to each amplifier.
Can you connect multiple amps together?
If pass-through functionality is available you can connect two or more amps together. You can connect pass-through output on the first amp to the preamp input on second amp and up to so on. It could be more complicated for you to understand the internal wiring if you have no technical knowledge.