Is there a way I can post a picture taken from my smartphone onto a
thread?
I've always just done it the old fashioned way. I take the picture with my phone, send myself an Email from my phone and include the photo as an attachment, open the Email on my computer and download the photo, and then I can post it in the forum.
I know there are "easier" ways such as using Dropbox, Google Drive, Photobucket, Instagram, blah blah, but that requires registering for accounts on those sites, downloading their proprietary app on your phone, learning how to use them, etc.