As Pete said, I was forced to transition from my old photo standby, Picasa to Google Photos (not Google +) when google bought out Picasa and then killed it. My many existing photos and albums were automatically put into Google Photos on the web. However much has changed, including background code on the photos that has changed my ability to post photos on MLS as easily as I used to. For example, I used to pop photos into ongoing chat, but that is no longer possible, as the photo web address is too long for the chat character limit (!) So for chat, I find another web based place to stash the picture and then post it.
As far as posting on an MLS thread, I go to Google Photos, click on the picture I want to post, then right click on it, and click on "copy image address". Then, back here, click on the yellow "insert image" icon, and add the address and hope for the best! As you can see, one issue is the size of the picture. I used to size photo properly in Picasa for insertion into threads in MLS to avoid having to scroll but the photo below is a little too big. So there is where I am, please feel free to ask any other questions if I can help, regards, Jerry