@truedwell - If you refer #9 of the "RULES AND CONDITIONS OF THE CONTEST", it says that participant can submit the entry on the contest page (you have to wait for the link to be active on August 3rd 2017 at 9 AM EST) in below format.
My entry for the #AFOFA contest - Subject - Invitation Code
[Picture] - If you want to add any picture.
Original Post link (Without original Steemit post link, entry will not be considered for voting, and will be commented by @cryptoqu33n as disqualified)
Request to vote (Maximum 50 words): Please vote my post because......
Link of the contest page [link]
That means, you just need to put link of your already existing post on the contest page in above format.