first problem...behringer....now the brand bashing is over...onto the next thing...
so TRS stands for Tip Ring Sleeve, which refers to a balanced audio cable. also defines how the cable is wired. positive tip, negative ring, and ground sleeve.
TS stands for Top Sleeve, which is a unbalanced audio cable. (often used in guitar/bass world and on speaker cable). wired as tip positive, and sleeve negative and ground.
TRS cables are considerably better to use in most practical circumstances where possible. for example, basses effect pedals, and amps, all use a TS connector, and would advice against. however "most" outboard effects proccessors, mixers, for all outputs (some inputs, for example an insert on a mixer) use TRS. this is because a TRS connector provides a cleaner signal and is less prone to ground noise since the negative wire is run separately from the ground.
also an XLR is a balance cable as well.
now for your setup instructions...lol
take the left and right XLR main outputs go to his amp, then to his main speakers (as per normal.
to connect the sub, take the left channel 1/4" TRS jack from right next to the XLR outputs, then go to the XLR input of the of the sub. and then control the volume from there. unfortunately i cant get a good enough picture of the back panel to give you much more detail from this.
the 8x "sub out" are not so you can connect 8 subs to the mixer. they are for the subgroups. so you can group together channels.
i hope this helps.