Looks like your integrated amp has a full range pair of pre-outs with no bass management so the LFE setting is out (the LFE setting would let your pre-amp manage the low pass filter, used in connection with the mono input labeled for such). Use a pair of rca cables to connect the L/R pre-outs on your amp to the rca L/R inputs on the sub.
Your sub's frequency range is not 40-140hz, that's the range of it's low pass filter (they call it a crossover but there's a separate set of dip switches for a high pass filter for your speakers....but don't see how with your integrated amp to take advantage of the high pass filter as your amp doesn't have main-ins or a processing/tape loop). Your sub specs an 11hz - 200hz range. Your R3 speakers spec a range of (-6dB) 38 hz - 50 khz, and at (-3dB) of 58 hz - 28 khz. Some like to set the sub's low pass filter near the -3dB point (58 hz in your case), some half an octave or more above that, but generally you don't want to go lower than the -3dB point. Since you don't have appropriate sub integration tools in the amp to help you set level or the low pass filter, you'll have to set them "by ear", which is not ideal.....or do you have an spl meter or measurement mic/software available to help?
Might check out this and the other suggested articles here
https://www.audioholics.com/subwoofer-setup/basic-subwoofer-setup
