Obviously you put your own stats in the area for your fighter.
To determine your opponents you need to figure out how many APs he has.
There are 2 ways - the long time consuming more accurate way, or the quick less accurate shortcut.
Long way - look at bonus points in the rules (go to help and then 'playing the game' and find the bonus points section). Learn there how many BPs a fighter gets for each time he raises his status.
Then go through all your opponents fights and add up the BPs he'd get. At the end you'll have an idea of how many APs he's gained. It's time consuming and I usually only do it in the most important matches.
Short way - fighter starts with 53 so add 53+rating+status and you'll get a number close to his # of APs. If he's a slugger with many KOs maybe add a point or two.
Once you have # of APs go to the commentary "Tools4TheTrade" and find the "Fight Doctor Scouting Tool." Punch in the # of APs, your opponent's height, weight and build and it will spit out an estimation of his AP spread.
You can tweak it by adding a point here and taking one away there until you got what you think he'd have.
Those are the numbers you should input into sparring for your opponent. As time goes by and you gain experience you'll learn to know better what your opponent's #s are likely to be.
Look through your opponent's past fights and make notes on what styles he uses, how many punches he throws, how many he lands, what he does in each round noting whether he's behind in the score or ahead.
It's best to look at his fights when he was fighting an opponent who is similar in stats to your fighter.
Look at 3-4 of his most recent fights against this style of fighter.
Does he always have the same fight plan? If so then you should be able to put it into sparring and keep working on your FP until you come up with one that beats it.
If it's not always the same plan does he have tendencies he uses over and over? Like does he always go to the body which makes him vulnerable to a head attack? Does he always rest in round 6 or always rests when he's ahead by 3 rounds? If so a perfectly timed allout might take him out.
Input what he's done in past fights into the sparring partner and see if you can beat it.
If not, fiddle around until you find something that does.