Oh okay, this'll be a long, bad explanation, but let's try. ^^"
First you go to you farm page and then search for scour areas in nearby places.
When you scour, there are few things you should know. First you have scour levels. My current scour level is 6 which means 7 is the max. number of simultaneous missions. What does that mean? That means you can max. send 7 Pokémon on a mission at the same time. I also have a 33% chance of getting a box in class A. The higher the number is, you have more chance to find a box on a scour mission. So basically, as your scour level goes up, the higher the numbers are - you can send more and more Pokémon at the same time and you have higher chance to get a box (you get experience when your Pokémon get back from scouring.)
Now, about sending Pokémon to scour. The main thing you want to know is the Pokémon's likes and dislikes. For an example, my female Glaceon likes Forest and I didn't check what are her dislikes. Likes and dislikes vary, so if you want to know what does your Pokémon like, you have to send them to every scour area until you find out its likes. Don't send Pokémon to areas they dislike, because then they won't be happy and probably won't find anything when scouring. If I send my Flareon to Ocean, he'll hate it because he dislikes it and won't come back with no item.
And ummm, that's pretty much it. The more you send your Pokémon, and often too, you get more experience, and when you get enough experience, you become a level higher scourer.
Did you understand everything? ^^"