Selecting a dripless candle is best, because there is less dripping and waxy mess down the sides that can get on the glass chimney.
Push the candle down firmly. The grips in the stake will groove the wax candle, holding it tightly in place.
Your final design size will be determined by how long you extend the greenery and flowers on the end.
If you have a smaller table, simply keep the greenery ends shorter and more compact.