Oven doors are built with two panes of glass in the window. Besides the obvious benefit of providing users a place to see the food without releasing heat, the two pieces of glass add extra insulation so that heat doesn't escape through the glass itself and protects the user from severe burn. The space of air between the glass panes is meant to keep the outer surface cooler and to trap heat that makes it past the first pane. Juices and steam sometimes make their way in between the glass and cause streaks. To clean them, you must take the door apart.
Open the oven door and look for the hinges that hold it in place. Remove the hinges to detach the door from the rest of the unit.
Lay the door down on a soft cloth so that the outside of the door is facing down.
Look for the screws that hold the door together. Unscrew them and set them aside. If might be a good idea to have sticky notes on hand so that you can label the parts that you remove. This way you will know where they go when you are finished.
Remove the inside panel of the door after you have taken out all the screws.
Set aside the insulation that is located inside the door. Mark where the pieces should be located.
Unscrew the interior panel that is holding the glass in place if there is one.
Take out the top piece of glass and clean it with glass cleaner. Clean the bottom piece where it is. There is no need to remove something if you do not have to.
Place the glass and then the panel back and screw it back together.
Insert the insulation as it says on your notes.
Put the back panel of the door in place and screw it all back together.
Re-attach the door to the oven at the hinges in the reverse manner that you removed it.