Status: Choose a room to begin.
Draw rectangle sets the size. Adjust lets you move the piece anywhere.
After you set the size, click Select Frame above the preview.
Next, click Adjustments to soften edges and dial in shadows.
When it looks good, click Export above the preview.
Export becomes available once you have a room, artwork, and a rectangle placed.
PNG is best for maximum crispness.
JPG is smaller and faster to share.