as mentioned above, learn the basics of magick before casting, it will help you with your success rate, as well as keep you safe.
after studying, try a simple candle spell. i suggest a luck or protection spell. take a candle of the corresponding colour [white for protection, green for luck] hold it and charge the candle with energy. be sure to visualize a glow of energy, as well as feel it [if you can't feel the energy there probably isn't any being pooled in the candle] when you feel ready, place the candle on your altar and light it, as it burns down, visualize your desired intent. [a white light protecting you, good things happening to you] be sure to let the candle burn out. if you decide to put it out for whatever reason, snuff the flame, blowing it out can undo the spell.
of course before you cast be sure you know how to charge/ground energy, cast circles, the moon phases, how magick works, and so on. as you advance with magick, you can add oils, runes, and other objects to candle spells, but this is a very basic one focusing on your ability with energy work.