You will go to the turnstile marked for breakfast reservations. A cast member will check your name from their list, and then you are allowed into the park. You then walk to the restaurant, which isn't very far from the main gates.
Nobody will escort you, but you aren't going to get too far away from the restaurant before someone stops you. The boundaries are from Prime Time Cafe up to Echo Lake. The other Echo Lake "exit" point by the boat is also cut off. After breakfast you will join a short holding line at this point, and as the park opens you will join the line once it gets to your spot. Cast members "walk" everyone down toward Toy Story so you ease into the line, and are right in front.