The Sub you get will ultimately determine how you hook it up.
The easiest hook up is gonna be "High Level Inputs," speaker wires run from the receiver to the sub and from the sub to the Receiver/Integrated Amp in your case. By and large "powered sub" tends to be the preferred choice for the most part. A powered sub takes the load of the Main Amp and then there is ported or sealed??
I have both and I tend to "prefer sealed" in larger subs; for music myself, but there are good units in either design. You did not give a budget (Yet??) But Parts Express has a unit that is relatively inexpensive.:
https://www.parts-express.com/dayton-audio-sub-1500-15-150-watt-powered-subwoofer--300-634
They have another that is about 50 bucks less but it only goes down to 50 hz, so not really worth the trouble with Heresy's with there smaller unit??
And there is always Cl if your OK with used?? You could find well just about anything locally "sub wise" near you perhaps?? And if your gonna spend real money ... PIA that it may be. You could ask if you could bring "your speakers" to try it out?? In any case if you buy "used" off Cl, you should "hear" it first. Bad plate amps with powered subs ... is not uncommon.