[swarmee]

You need to upload them to a photo sharing website first. I use Facebook, since the images stay very large and clear. One downside is the images seem to disappear from the threads after a few months.
IMGUR, IMGBB, etc are supposedly better.

Then you click the yellow sky over mountain button at the top of the text box, then paste (making sure to overwrite the automatically filled in https:// ) with the full URL of the photo location on a different website. That will embed it in your post instead of attaching it.

Some people also have better luck logging on the tapatalk app if they're using cellphones.