See Craig Epifanio's legal guide on the Avvo website. It will be a great start for you. The problem may be that you can only seal or expunge cases out of a single incident. If the two possession happend on different dates, you may only be able to do one.
You are probably only going to be able to remove one of the two from your record and you also can not have been convicted of either of these or any other criminal charge. Check out my website below and it may answer some of your questions.