If more than 4 hours have passed from the time you originally posted it, you can "report" it to a moderator and simply ask them to delete it. To report a post, try the icons until you find the right one? It will have instructions. On my phone, its a red outlined white triangle with a black exclamation point inside.

Otherwise edit your post, and one of the options will be delete. Its a two step process. Hope this helps.