I'm now 3 weeks post RARP and like you wasn't given any catheter instruction. At the point the catheter was removed I mentioned it and then was told how to deal with the bag overnight! Leave the day bag connected, and connect the night bag which sits at the end of the bed on its stand. When you attach the two it's worth leaving some urine in the day bag to make sure the flow into the night bag is working. They said there's no need to strap the day bag on, just let it drop over the bed but of course leave the thigh strap attached. Change the day bag every 7 days as well as the night bag. I also found that during the day changing legs is well worth doing because the thigh strap caused a really itchy rash and having relief from that during the daytime helped as did 1% hydrocortisone cream (2.5% was better used sparingly if you can get it). I also wiped down the catheter tube from penis to day bag with medical grade 0% alcohol anti-viral anti-bacterial wipes.
I had mine out 15 days after surgery and whilst I counted down each day it really wasn't nearly as bad as I thought.
I had bi-lateral nerve sparing, retzius sparing surgery using the da Vinci SP robot and I've been fully continent after a couple of hours post catheter removal.
Good luck in your journey