I think the OP just got adsense. since I was really slow on the uptake - I'll try to post my knowledge...
-you cannot monetize JUST gameplay (contrary to what others tell you, you CAN monetize gameplay commentaries and montages, as long as you have the rights to whatever you include in your video (there are good sites for royalty free music))
-of course do not expect to monetize someone else's work, in fact don't even upload it
-adsense will not pay out until your balance reaches $100 which WILL take forever. DO NOT TRY TO CHEAT ADSENSE OR HAVE YOUR FRIENDS CLICK BOMB YOU! you WILL get banned!
-sometimes videos will sit on the considering monetization a long time, a good way to monetize your video INSTANTLY (I found) is this
-INstream ads vs INvideo ads: instream ads show as trailers BEFORE your video and invideo ads show as box on bottom of your video. people DO NOT like instream ads. in fact about 60-70% of people will exit out of the video when they see an ad before it. BUT they bring in much more $$$ then invideo ads. it's your choice.
-videos over 15 min in length (you will sometimes have to work toward this goal) will give you the option to insert midroll ads and post roll ads. post roll ads IMO are redundant. no one will watch them anyway. midroll ads are a good idea because you can then turn off those pesky PREroll ads that people hate. NOTE: there must be at least 7min between ads and you can insert as many of them as you like, if your video is long enough.