is it possible to connect a subwoofer to Crown XLS amps?

huh? can I not share the speaker level connections with either an REL sub or another sub that accepts high level?

will be used as an integrated amp to drive Magnepan LRS'
the amp actually has built dsp crossover functionality

sorry, I can see how my post might read funny
I've never done a speaker level connection from amp to sub
I've read of people with tube amps using different taps, and guys with a/b sections on stereo receivers using the second set of speaker terminals
a little confused on how to share the same set of terminals

should I use spade connections to share with the current bannana terminals?  never used anything but bannanas before so a little worried about screwing this up

again, amp will be used as an integrated to power passive speakers, sub would be self powered
2.1 stereo system