Measure the width and height of the window glass with a measuring tape. Make sure your grids match these measurements.
Assemble the grid's pieces and insert the connectors on the ends of the grid pieces according to the manufacturer's instructions. Some connectors are plastic; others are metal pieces with points inserted into the wood frame to hold the grid in place.
Place the grids against the glass in the window, centering it so the ends meet the edge of the window frame. Follow the manufacturer's instructions for affixing the connectors to the edge of the window frame.