By default, the platform does not have this option. You can use the following CSS code to show a full-size image of the Single Post featured image.

Please follow the steps below:

1. Go to BuddyBoss > Theme Options

2. Under Custom Codes, enable CSS

3. Append the following:

body.single-post .entry-content-wrap .entry-img img{
    position: relative
}

body.single-post .entry-content-wrap .entry-img, 
body.single .post.full-fi figure.entry-img, 
body.single .post.full-fi-invert figure.entry-img {
  padding-top: 0;
}

4. Save changes 

Note: Any modifications are considered as custom work already. Know more about our Support policy here: https://www.buddyboss.com/support-policy/