As you are replacing the glass with screen you have to replace the spline too as the grooves have to be specific to the thickness of the screen which varies from the thickness of the glass used in storm doors.
Storm door screen glass change.
Inspect the storm door to determine if any hardware is needed to swap the glass for the screen.
Now fix the newly cut screen into the grooves of the new glazing spline.
How to change the glass to screen in a storm door step 1.
The glass or insect screen are secured using removable retainer strips on the interior of the door panel.
In storm doors the glass of the windows is separated from the door frame by a glazing spline.
Clean it off on both sides with a hose if necessary.
Then fit the glazing spine into the opening in the storm door and put back the screws.
Do not pull the retainer strip towards you as this will crimp the retainer strip and may damage the retaining system.
Slide it into the door channel in front of the screen.
It should not go in between the screen and the door frame.
Start at the top of the door and hold the retainer at about a 45 degree angle with the edge with writing on it facing you.
Retrieve the screen inset from wherever you stored it.
To switch your storm door glass panel to your insect screen or vice versa follow the instructions provided in the youtube video and written instructions below.
Remove the glass and place the screen in the door opening.