To get an Aisler coupon you have to draw an rectangle on the silkscreen layer with predefined sizes as shown in this Aisler Community post.
Using fritzing for pcb design there is a problem. There is no line draw part to place the rectangle on the silkscreen.
Instead you have to draw a rectangle with inkscape and import it into a silkscreen image part.
As example you find a *.svg file here:
Size: 30 x 7.5 mm (minimum required size). Use the browsers “Save image as” function to download the file.
Hope that helps others.