Congratulations on your decision to buy a home! Yes, your first step is to speak with a loan officer who will review your credit with you and help you get the best rate and terms. Your loan officer will discuss with you your comfort level with the payment and together you and the loan officer will decide what price range you should be shopping in.
Regarding your down payment, yes, 3.5% is usually the minimum with the most popular first time home buyer program. In my area, we also have wonderful down payment assistance programs that will help you even get in for less than 3.5% of the purchase price.
Make sure your loan officer is in or near the area you want to buy in. A loan officer in LA is not going to be familiar with down payment assistance programs in Riverside for example.
Finally, when you are ready to shop, get an agent who specializes in first time home buyers. You have different needs than someone who has bought 10 other homes. Also, make sure your agent is in or near the area you want to buy in. There will be many trips out to the house for inspections, appraisals, you want your agent to be accessible.
Hope that helps, and good luck in your search.