You have to upload it onto a host website first. Get onto your photo album on Pinkbike, and you will see "upload photos" above where it shows what page you are on.
YOU can not delete a picture yourself, but you can make it so other can not see it. To do this go to your "Photos" section on your profile and move the pictures you want into the "Trash" Folder.
The only way of actually deleting a photo off the site is by asking a mod to do it for you, but you should only do that if you are desperate to get it off the site.