To make gold teeth, take a dental mold of your teeth, allow it to harden and then wrap gold sheeting over the mold. Warm the sheeting so that it is malleable, and create a tight impression of the molded teeth. Allow that to harden, and remove from it the dental mold.
A dental mold may be purchased at any drugstore or ordered from online sites that cater to dental needs. Gold sheeting is also available online or from jewelry and craft shops. It might take some practice to create the right look, since the gold sheeting needs to be fitted at the right thickness to make it neither too thick or too thin over the mold. If the gold is too thick, it might interfere with talking or eating. If it is too thin, it may not be sturdy enough to hold together inside your mouth.
Keeping the gold soft can be a challenge. It's not necessary to melt it to a liquid state, but it has to be soft enough to work with. If you're not comfortable using soldering equipment to soften the metal, get some instruction, or consult someone with experience who can show you how to use it.