You can't enter the barn on 24 Carrot Island, but you can enter the abandoned house right next to it through the chimney.
To open the attic of the Mill on Astro Knights Island, see the related question.
Where is the warehouse on poptropica's spy island?
ON THE ROOF
just click on him
he is in the warehouse that has the lights.
Use the crowbar to open the sewage pipe tp enter the warehouse on 24 Carrot Island.
you must get adecoder and answer all of the peoples assignments they have for you then after you do that you can get in
you use the carrot transporter that you got in the beginning
Get the crowbar and pry open the sewage pipe and tada youre in
get the invisible suit on and go past them
Use the camoflage suit and sneak past the guards while they're not looking.
The person you can hire on Bouffant bay is inside the warehouse. He will cost you about 15,000 doubloons.
There is that building that shocks you, so you jump window to window until you get to the top and then you have to get you laser pen and laser the window thing and go inside.