I'm not sure if you need a course. If you have a radar, turn it on when you can see things (don't need it) and you'll understand how it works more or less. Check with your local power squadron to see if they have a course if you feel you need it. USPS Educational Department - Marine RADAR
Mine is old, from back in the days of CRTs and before cheep computerised electronics. aimed originally at the professional rather than yachts.
I think there are more up to date editions. But they are ridiculously expensive. Cheaper to by a RADAR and read the instructions. you can find free on line.
The RYA has a version aimed at yachts. "RYA Introduction to RADAR" by Tim Bartlet its only about 32 pages and based on RYA 1 day RADAR course. About 10 bucks used on line
They also have a RADAR simulator cd quite expensive though 62 pounds
There is one called "Radar Made Simple For Cruisers" by a retired USN Comander T.L. Sparks. it even claims to be aimed at the single handed sailor. its around 20 bucks used on line.