Are you talking about attaching a photo to a post?
Attachments are disallowed for social. You need to upload the pic, either to your BL gallery, or a photo hosting site. Then you can post a pic by using the img button in reply, by putting the photo url in.
Me last night at our "book club" girl's night. They loved my hair and wanted to make me into Princess Leah.... unfortunately we could only find two hair ties so it was a bit messy.