If it is lighter behind you than the outside, they will still see you. So if you have it on the shadow side of the home with light streaming in through your door they will still see into the room.
You can get it on Amazon/eBay easy enough. Buy larger than you need in case of tear/shrinkage/ and trying to get the two parts to separate.
Putting a slice of sticky tape on each sheet makes them easier to separate. Thoroughly clean the window first, including the rubber. Spray the window with a soapy solution. As you separate the sheets, spray them so they stick to nothing. Lay the sheet on the glass and gently ease the water out. If you have to rush it then you should not have started it.
Leave to dry before trimming
