You don't need to use a specific form to cancel. Under Hawaii state law, all you have to do is send Marriott a letter notifying them that you are canceling the purchase. The materials you received from Marriott should list the address.
I'm assuming it has been less than seven days since you signed the contract. If more than that, unless you have just now received the disclosure statement, you're probably out of luck.
See this PDF (you'll need Acrobat Reader)
Q&A from the Hawaii Department of Commerce and Consumer Affairs for more info.
When you send the letter, you should send it certified (receipt requested) as proof of your timely cancellation.
Just received my Marriott stuff from Waiohai in the post and found that there is no TS-10 form to use for rescission. Does anyone have a copy that I can use or retype. Went to Hawaii DCCA website but they don't seem to have it online.