How can U melt candle wax already inside a jar to add another wick?

Try melting wax in a double boiler. Put a wick in the candle pour the wax into the jar.

If you want to mix the wax that is in the jar, try putting the jar in a pot of boiling water until the wax is melted then mix the wax from the jar with the wax you have melted in the double boiler.

Good Luck

Use the double boiler method, bring a pot of water to a boil, turn off the flame under the pot, place the candle in the pot and swirl it around alittle to get the wax moving so the wax in the middle melts too. (Only if its in a glass jar)

Warm oven.

candle warmer my mom does that