Is it just the trailmanor, or is it 'any' trailer towing that you don't have experience with?
If it's any trailer, then I would suggest practicing in a big empty(ish) parking lot, like maybe a mall or something on a sunday morning. You can drive up and down the lanes in the parking lot, and practice turning, where you will be able to get the hang of how the trailer pulls behind you. You'll need to fully understand (with practice) of how the trailer tracks behind the tow vehicle, and how wide you will need to make turns in order for the trailer to come around with you, without running it up over curbs, or other vehicles.
You could take some plastic orange cones to set up, and practice turning around them, or even backing the trailer in between them (which is the advanced course
).
Make sure to adjust the mirrors to fit you, not your boyfriend. Your mirrors are your best friends when towing trailers. Set the mirrors where you can see the sides of the trailer and the tires, while you are practicing. You can then look in the mirror when making the turns, to see exactly where the trailer tires are going across the lines at. Practice widening your turns out with the tow vehicle, until you get the trailer to turn where it needs to. You can also see where you need to keep the tow vehicle centered in a lane, to keep the trailer centered. Most times the trailer is going to be wider than the tow vehicle (TV), so you don't want to let the TV get too close to the side of a lane, because the trailer will be OVER the side of the lane
Just take it slow and easy. If you run over a marked line in the parking lot, it won't hurt a thing.
It won't take long, and you should have a good feel for it. It just takes some experience.