Let a Lowe's expert show you how to install bi-fold doors. Learn how to install bi-fold doors that you can add to you closets. Get your drill, doors, tape measure and other tools together so you can be ready to complete your project. Measure your closets so you know what kind of door you need to fit your projects. If you need to paint, paint before you add to the door. Mark all your spots and measure before you add your pieces.