I took my younger dog on a couple of courses and she had a great time.
The principle is pretty simple: introduce the dog to a scented item (eg a small toy that's been in a box with some soap for half an hour. Or a dirty sock plucked from the floordrobe of a teenaged DC. Or whatever).
Let the dog have a good sniff and then get it all excited about it. Leave the dog, go out of sight and tuck the item just out of sight e.g. under a sofa or behind a chair.
Let the dog in, give a command like 'find it!' and encourage it to sniff around by directing it along the sides of the room and around the furniture. Make the first search quick and easy and give loads of praise and maybe a treat for a successful find. The dog will learn in time to start the search alone and I imagine if you do it enough will work out its own search pattern.
You can also do it in the garden, or teach a dog to hunt for concealed tennis balls in grass and bushes.
Some dogs will have no interest in a scented item and you'll have to get them to search for treats or cheese.
I do it at home when I need to quickly take the edge off a dog's energy, or one needs a short walk and it's wet and cold and I'm short of time.