Add wax to the canister, and place it into a pot half-filled with water (there should be at least 15cm of water around the canister). Heat the water to melt the wax, but don't bring it to a boil. The wax shouldn't be heated above 75°C (167°F).
Beeswax or soy wax
Begin by dipping a length of wick and then use your fingers pull it* straight. Leave to cool for about a minute then drip again and let cool. Continue to dip and hang to dry, for about 2 minutes each dip, until the candle is as thick as you want. Add more wax as needed to maintain the wax level in the canister.
Cotton or hemp wicking
Alternatively you can dip your candle into wax then cold water to set it faster, but make sure your candle has no beads of water before adding it back into the wax, or the wax won't stick properly. I like to gently rub my hand down the candle to knock off any excess water.
Once the candles are as large as you'd like and fully dry, trim the wicks with scissors. You can leave them long for gifting if you'd like, and they can be trimmed later.
Cut the bottoms of the candles off with a sharp knife if you want a flat base. This wax can be reused. Let the candles cure for at least a couple weeks, preferably a few months, before burning.