To fix the side-view mirror of a car, remove the old glass and stick the replacement glass if it's a manual mirror. For an electric mirror, detach the old assembly by removing the screws and disconnecting the wires and replace it with a new mirror assembly.
If the glass of a manual mirror is broken, pry it off with gloved hands. Remove the back peel of the replacement glass bought from an auto parts shop and stick the glass in place.
For cars with an electric mirror, buy a new assembly from an auto parts shop, junkyard or dealership. To remove the old assembly, open the car door and locate the triangle-shaped access panel on the mirror's side. Unscrew the panel to remove it. If no screws are present, pry the panel off using a flat-head screwdriver. Unclip the wiring harness under the access panel, avoiding cutting any wires. Remove the bolts keeping the mirror in its position, and gently pull the old mirror away. Insert the wires of the new mirror through the holes, connect them appropriately to the harness and replace the bolts. Test if the mirror works and then replace the access panel by screwing it back in or pushing it into place.