You have to finish all of the quests in Krokotopia (including the Krokosphinx and Tomb of Storms) and get permission from Sergeant Major Talbot in order to go to Marleybone.
If you need to go there to buy a specific item (such as the Troll's Ear Pendant, which can be used by a level 10 wizard), you can try asking a higher-level friend to go to Marleybone, and let you teleport. Otherwise, you can often find items for sale at the Bazaar.
. Do i need to be a certain lvl? I really need some help 
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