Sue,
The first step is to decide how many days you want to stay at Disney. Book your hotel room first. Disney will not hold your wedding date or location until they know that you have a reservation at one of their resorts. If you want to stay the amount of days that Disney offers you can choose to book your wedding and accomodations all at one time.
Actually, the first thing you should do is decide the location where you want your ceremony to take place. Remember to look at the pros and cons for each location. As soon as you reserve your time and place choose an officiant right away as they get booked fast. Congrats on your wedding! Keep your planning questions coming. We all on here just love helping out and giving our two cents! lol.