Listen, no offense but no one, including myself, will write a step by step paragraph about how to beat "Mythology Island". But, I am nice enough to give you a tip; try watching video walk-throughs. You can see what you are missing.
On each island in Poptropica, you must complete the island quest to earn the Island Medallion. In 2009, the completion also awarded 100 Poptropica credits per island.
Early Poptropica, and Spy Island.
Complete a mission on a island like Early Poptropica
You would have to specify the island you are asking about.
You complete all the necessary tasks.
Look at this.Poptropicasecrets.com
You have to complete the island to unlock that surprise.
The easiest island to complete is Early Poptropica.See the related question below for the guide.
To leave, use the Poptropica blimp on Main Street. (To complete the island, see the related question.)
you complete quests and earn medals then go on to the next island
You complete it and get the jewel