Hello,
you need to lit it some time before use (about 10-15minutes) so they can melt. They do produce bit of smell when burning, depending on the choosen scent. After that you pour it on the skin, from bit of high, but the product is not overly hot.
Also there was a video with some of the candles, the bigger versions. Just not sure if it still functional.
They are good. the hot massage feels lovely. Also some will nicely moisturised your skin, better than body lotion. For this reason they are extremely lovely for my skin, as they nourish it deep and it stays that way. So if your skin is dry, it may also like this aspect of them.