you dont
depending on the jail if you mean the one on conterfeit island you answer the detectives questions correctly if you mean the on on ghost story island you leave the prison and go to the lighthouse
The seagull keeps you away from the (broken) school bell on the clock tower. To get rid of it, you'll need to get a lobster to use as pliers to turn the lighthouse light. (see related question) * Go to Puffin Point and catch the blowing photograph. Swap it for scuba gear at the photo shop, and dive by the lighthouse to recover Cap'n Salty's lost lobster trap. Climb up to the top of the Lighthouse and click use for the Lobster. Now the light will shine towards the school and the seagull will leave.
I don't think you can leave an island with a horse.
go to the lighthouse.
On every island, the Poptropica blimp is above Main Street. To leave Nabooti Island, return to Nabooti and walk right from the Museum.
you just get in the plane
any planet
If you have the Bell Clapper from the secret room behind the file cabinet, you need to use it to fix the bell on the school roof. You will need to get rid of the seagull there. Get the photo that is blowing around near the left side of the lighthouse, and swap it for diving gear at the Say Cheese shop. Dive near the lighthouse and recover Cap'n Salty's lobster trap. Use the lobster as pliers to turn the light in the lighthouse toward the school, scaring off the seagull. One you repair the bell, use Cap'n Salty's jet skis. From the top of the lighthouse, you can use the telescope to see a strange Seal island to the right of Puffin Point.
To leave, use the Poptropica blimp on Main Street. (To complete the island, see the related question.)
Wait for principal to leave then you leave
Leave the castle, enter the city, and jump up into the blimp.
You click on the boat near where you came