That's tech-talk for 'read the Manual'. Some amps have a 'bridging' option. If you run stereo, you can use one bridged amp for each channel. Otherwise you'll have to bi-amp your PA rig. This means using a crossover unit to divide the audio signal into low & high frequencies. The low freqencies go to your most powerful amp, which is then connected to the low-frequency speakers. The high frequencies go to the other amp, which drives the horns or tweeters.
If you can't bridge your present amp with another one, or split up your speakers for bi-amping, you are definitely S.O.L. (That's more tech-talk). ;)