I'll try to help.
Click on edit post. That will bring this up. Click where my cursor is in the below pic..
That should bring up this window...click on "from computer"
Then hit the "choose file" button. This will bring up files where you have pics on your computer or phone. I can't help you find them but assuming you find it on your device, click it and then hit the "upload files" button right below choose file button. That should do it. Just hit the "save changes" button at the lower right area to save the picour post. post.
Try that and see if it works for ya. It did for me.