@keven1508 - Film based one-way mirrors are a compromise. They’re marginal at best if you’re on a tight budget. The amount of light reflected just isn’t as good as a professionally built one-way glass.

If you do insist on going with film, I would recommend taking the film and the glass to an automobile tint shop and asking if they’ll apply the film for you for a nominal fee. They have the experience and are probably the best people local to you to do it.