Renato Lond CerqueiraMission achieved: people think Masto is a cat pic sharing site! 
Mike From UK@renatolond How are you adding descriptions to your pics? "A screenshot of a tweet..."(!)
@michaelfromuk If you are in the web (or using the web client from your phone), after you add a picture, there's a space under the image to add the description, like so:
@renatolond Thanks! First day on. I uploaded photo earlier and was looking, but didn't think to hover over pic. Cool :)
@michaelfromuk No problem, welcome! 😄