When you click on the restaurant that you want to book an ADR look right above the date and you will see a box that says Update Your Profile. Read the second line inside that box and click on the words "retrieve your reservation"
You will need your reservation confirmation number.
90 + 10 refers to the 'window' of when you can make your reservations. If I'm not mistaken, if you have a valid 'onsite' reservation you can make your ADR at 90 days '+10' from the beginning date of your reservation instead of the regular 90 days.
If you're staying onsite, on the 90 day out mark from your arrival date, you are able to book your ADRs for the first 10 days of your stay (instead of having to call/go online each day and make the ADR for each day of your stay)
Dreams Unlimited Travel is committed to providing you with the very best vacation planning experience possible. Our Vacation Planners are experts and will share their honest advice to help you have a magical vacation.