One quick search in the message boards would have given you your answer, young Wizard.
Much like reading a chapter book, Wizard101 is sequential game play (before you move to level 2 you must complete level 1). Even if you have purchased a Membership you must first complete all of the quests in one world to be able to move on to the next. The same thing goes for Access to some of the streets or areas within a world. For instance, when you've successfully completed the quests for Wizard City you will be given a quest to enter into the next world, Krokotopia. Once you have your own access there, as long as you have a Membership or have purchased the Premium area with Crowns, you will be able to enter that world freely.
Are you a starter of this game? if you are, it's ok to not know. When you start off the game, you will get a line of quests followed by another one. Complete Unicorn Way, and then when you get to that sergeant Muldoon i think that's in olde town, he tells you to defeat lady blackhope, he allows you to pass through triton avenue, but after, when you talk to him, he has three quests in a list for you. Each of them will lead to firecat alley, triton avenue, and cyclops lane which are in also olde town.
Complete all of those streets, and one of those quests will lead you to merle ambrose, which will then give you 2 quests to choose from. one is colossus trouble- side quest, was a mistake for me. but the other is " a look of horror". -main quest, defeat foulgaze in olde town, after, ambrose will tell you to defeat lord nightshade in haunted cave, and then he will tell you to explore the door behind the waterfall, which is the death school. "gasp" but my favorite part is when u get the new spell for completing the quest. anyway locate it, explore inside death school, talk to dworgyn the death assistant professor. then merles gives u a quest to ......