Step one; meet with a qualified Loan Officer, either at your bank or through a broker. Tell them you want to get pre-qualified or create a plan so that it can happen soon. A good lender can give you legitimate tips on improving your credit score, which would either get you approved, or improve your rate. I am a lender as well as a Realtor and I have done this for several clients. I don't do FHA, so I can't speak specifically to their guidlines.
Your job time is good; the income is fine, so if you are not approved, it will be due to your score. Some tips for improving your score would be to keep lines open, but keep balances low. You have to use credit to build it. If you don't have any credit cards right now, apply for one at your bank or credit union. Ask for a collateralized card if you are declined. This means your limit would be capped by money you currently have on deposit there. Use the card, but pay it off monthly.
Beware of credit improvement schemes that charge you any money. I am not aware of any legitimate ones and you can do it yourself. The exception to this would be a rapid rescore through a licensed lender. You can do this, it takes some time, but less than you might think, and a little discipline.
I hope this helps.