Find Multiple Exposure in your camera's shooting menu (most mirrorless bodies have it). Set it to Additive or Average depending on how much bleed you want. Additive is more aggressive - highlights stack and burn. Average is subtler.

Shoot your first frame. The camera holds it as an overlay. Compose your second shot with that ghost in mind. Faces over architecture. Crowds over empty space. Texture over portraits.

Watch for: tonal separation between the two frames - if they're too similar in brightness, they'll merge into mud. High contrast subjects work best for the first frame.