Here is your one of your image codes;
*img]https://i.imgur.com/UG1xT2u.jpg[/img*
*I took out the brackets to illustrate the point without the picture
After the image ID ( UG1xT2u in this case) insert an s for small, m for medium or l for large. In this instance, I changed the image to medium so it now looks like this;
*img]https://i.imgur.com/UG1xT2um.jpg[/img*