To resize a Linear or Area (including Area Backout) object, select the object. You will see handles (small boxes in fact) at either end of a linear object and at each corner of an area object.
Hover your cursor directly over the handle you want to resize to bring up a Resize cursor, which will either look like or depending on the orientation of the object.
When the Resize cursor comes up, click on the object handle and move the cursor either in or out, up or down, depending on object orientation to resize the object.
When resizing an Area takeoff, you can grab one of the corners of the takeoff object to extend a segment, or, in the middle of a segment to move the segment in/out.
Attachment conditions cannot be individually resized on the Image tab. If you have a door as an attachment, for instance, and you want to make this particular door a different size, you have to go that particular Attachment condition’s Condition Properties dialog to change the size.
Doing this will change the size for all objects of this condition type. To change the size of a particular attachment, you must create a new Attachment condition for that particular size and re-assign the original takeoff to the new Condition. See Reassigning Takeoff Objects to a Different Condition.