How can I add a new wick to a candle in a tall container?

Try putting a candle in the freezer overnight. The cold should cause the wax to contract from the sides of the jar.

The easiest way, that I know of, to remove a left-over candle from a container is to put a few ice cubes on top of the left-over candle, wait a little while, and when the candle "pulls away" from the container, slide it out. If the top of the container is smaller than the rest of it, use a knife to cut the wax into size pieces that can be "dumped out."

http://www.ebay.com/gds/Top-5-Ways-to-Remove-Candle-Wax-from-Jars-/10000000178589930/g.html

You could always melt the wax, put in a new long wick and the wax from the two candles will give you a full jar candle to reuse again. Hello from South East Minnesota. I didn't think Minneapolis was considered in the northern part of the state.

Put the jar into a pan with water, heat the pan and the jar at the same time so that it doesn't break the glass. It should melt the wax for you. You can get the candle wick anywhere you can get candle supplies. Put a drop of wax in the bottom to hold the wick and holder down and a pencil to hold the wick above the jar. Then you pour in the wax to fill the jar. If you melt down both at the same time, you can just pour in both to make one as full as you want. Just watch when you handle the jar to pour the wax, it is hot and you want to protect your hands from the hot jar and the hot wax. I hope this helps, any other questions, just ask!