I wouldn't advise you to use the Tape Out as suggested. The subwoofer won't turn up when you turn up the volume. The only way for it to function properly is to just use the speaker wire connections with that amplifier.
You can go one of two ways:
Speakers and sub into Speaker Set A
Speakers into Speaker Set A, Sub into Speaker Set B
Both will work just fine. With them on two seperate channels (A and B), you will have the option to turn one set off (speakers or subwoofer). With them wired both to Set A, you won't have that option, but you'll have Set B available for future full range speakers (if desired).