How should a Virgin prepare for a foursome?

short story I'm in a polygamy(?) relationship and just moved in to live with my BF and other partners for 3 days now. He has 3 GFs including me and we're all virgin, him included. You may not believe it that's fine, but no ragebait or other troll pls. I am seeking a serious answer and genuinely wonder what and how should my BF prepare for sex in the next 2 weeks? I have read about girl preparation that we should be able to goon with 3 fingers and we are getting there but what about a guy? I'm helping him do a research so we can have a wonderful and unforgettable time together. He is well build but I doubt he would last, what should he or us practice before doing real penetration? anyone experience can give an advice?