Gather these parts

Peel off the protective paper and superglue the acrylic detail sheet to the back of the MDF window sheet

Glue the strip into the slots and the window frames onto the plate

Gather these parts

Glue the strip into the slots

Gather these parts

Slide the side panels onto the front panel

Slide the back panel onto the sides

Glue the center plate into the bottom

Glue the wall frame onto the bottom around the center plate

Glue the top on to the wall so that the wide slot is over the gap adjacent to the acrylic details sheet

Gather all these parts

Glue them all into the slots on the back of the window as shown above

This is where you can insert the acrylic after painting is complete.  Use glass froster spraypaint if you would prefer a matte finish window.

The top can be left un-glued so that the acrylic can be removed if desired