You should probably post support questions here:
https://bitcointalk.org/index.php?topic=18313.0Quick answer is that if you use run_p2pool with -a [ADDRESS], bitcoins mined will go to [ADDRESS]. If you don't define an address, p2pool will create a new address in your wallet named "p2pool" and newly mined coins will go there.
If a user logs into your p2pool with the user name -a [USER_ADDRESS], coins will go to [USER_ADDRESS] instead of what you set as the address. You can also set p2pool to charge such a user a fee for mining on your pool, if you'd like.