I don't know if you mean the Tomb of Storms or the Temple of Storms. Both are inside the Well of Spirits, which is only accessible after you've completed the storyline quests for Pyramid of the Sun and Krokosphinx.
When those are done, you need to light up the beetles on the three obelisks. After about 20 seconds, the portal will rise from the circle. About 10 more seconds after that, the force-field will allow you inside.
Inside, the Temple of Storms itself (an instance) is only accessible when you have a quest that asks you to go in there.