Product: FileMaker Pro
"I have bento for mac"
These are two different products. In which one did you "insert an image box"?
If this is bento, you'll get a quicker answer in the Bento forum instead of the Filemaker Pro forum.
Thank you for your post, and I apologize for the late reply.
In Form View, see if there is a lock in the bottom right corner of the window. If closed, that means the Form is locked and you can't make any changes. To unlock the Form, just click on the lock so it displays "Form Unlocked". Once the Form is unlocked, click just above the Image Box so three handles appear around the Image Box: right side, bottom edge, and bottom-right corner. Press the delete key to remove the Image Box. If you want the Form locked again, then click the lock in the bottom corner so the lock closes and it says "Form Locked".
Let me know if you need additional clarification.
In the future, please post Bento questions to the Bento forum at: