What a cutie. Congratulations. Such great personalities and so much fun. Having two myself, I'm rather fond of them. Still, I'm no expert but lots of good advice so far. Be patient and very consistent. Out first thing every morning. Might even begin by placing him where you want him to go the first few times. Praises when he goes. Some suggest associating a word or two like "go potty", "get busy", etc. so he learns what you're expecting. Mealtimes at the same time every day and out to the yard after each meal. Some suggest "crate training" where they start by sleeping in a crate and as soon as they get up they go out. The idea being that they won't soil the area they sleep in. I didn't have much success with it (probably because I wasn't consistent enough). I'm sure I was not a very good trainer, it took us about a week to two weeks before there were no more "accidents". You should be able to find a boxer specific magazine at the feed store which will have a lot of pointers. Have fun and enjoy your new housemate.