OPP is telling drivers to remember the following rules when using roundabouts:
When entering a roundabout:
Visual checks: Do visual checks of all vehicles already in the roundabout and those waiting to enter (including cyclists).
Look left: Traffic in the roundabout has the right-of-way. When preparing to enter the roundabout, pay special attention to the vehicles to your left. Adjust your speed or stop at the yield sign if necessary.
Adequate gap: Watch for a safe opportunity to enter the roundabout. Enter when there is an adequate gap in the circulating traffic flow. Don't enter directly beside another already in the roundabout, as that may be exiting at the next exit.
Travel counterclockwise: Once in the roundabout, always keep to the right of the central island and travel in a counterclockwise direction.
Keep moving: Once you are in the roundabout, do not stop except to avoid a collision; you have the right-of-way over entering traffic. Do not change lanes while in the roundabout. If in the inside lane and you miss your exit, you must continue around until you meet your exit again.
When exiting a roundabout:
Signal: Be sure to signal your exit and watch for pedestrians.
Maintain your lane: Stay to the left if you entered from the left lane or stay to the right if you entered from the right lane.
Maintain your position: Maintain your position relative to other vehicles.
Signal intent to exit: Once you have passed the exit before the one you want, use your right-turn signal.
Left lane exit: If exiting from the left lane, watch out for vehicles on the right that continue to circulate around the roundabout.
It seems crazy to me that some people find roundabouts so hard. I've always found them pretty intuitive but I'm definitely biased, when I was learning to drive there were about 8 roundabouts of various sizes near my house and I'd invariably have to take at least 3 at the start of any journey.
It's probably just because we're so used to them here but pretty much everyone seems to know how they work. Off the top of my head the only exception is one badly designed roundabout where you're meant to stay in the outer lane unless you're taking one exit that's practically a u-turn, people always take the inner lane (like you'd normally do) and have to change last second.
Depending where you live, roundabouts might still be a very rare thing to encounter, and the majority of local drivers might have never had to deal with one before.
Way back when I got my licence, they weren't a subject mentioned in the instruction or on the test.