You have to ask a moderator to delete a thread. However, you can add a poll any time to a thread. However at GS, well like all polls to be in the Voting Booth folder.
I added one to your Lady costume thread. If you edit your first post on the thread, you should be able to edit the poll to have the choices you intended.
Try adding a poll to this thread for practice! You start the thread. Then you can add your poll.
Click on Thread Tools in the top bar. Pick Add A poll from the list that drops down. Change the number of options from 2 to the number you want. Hit update to add the extra blanks. Type in your question, and the options you want. Put the close after number of days at 0 to keep the poll open indefinitely.
At the bottom, check multiple answers if you want to allow them. Click Preview to see if it looks right. Then click submit new poll & you're done!