Now that you have done the basic research and have an idea as to who you are, you need to start fleshing out your character. To create a fully rounded persona, consider for a moment all of the things that one must know to survive in the late 20th century. There is your food, clothing, shelter and any of a myriad of other details that you must be aware of to live in a culture. Now project those details back 400 years. These are the same sorts of things that you must know to bring a period persona to life.
Lets take an example.
You will need money on which to live. These are just a small sampling of the issues you need to know about. To do a credible job at your impression it is probably best to limit your interpretation to a middle or lower class character. The attitudes and experiences of the gentry and nobility are so far removed from our modern experience that it would be very difficult to do a convincing portrayal. To help put yourself in the mindset of a person of the period it really helps to read diaries and letters.