Cook with it. Use oil / fat.
Honestly, cast iron is about the most forgiving cooking surface you will find. People love to make it more difficult than it is.
Edit:
Some additional tips on cast iron:
Setting 4 / 10 (slightly below medium) is the default heat setting, and you have to really have something specific in mind to ever go above 5. I find that people who are used to teflon pans like to go up into the medium-high range. Things don't end well up there with cast iron.
Also buy a metal spatula. You aren't going to hurt anything, and it will be a more satisfying cooking experience. Plastic + cast iron is just going to leave you with a melted spatula. There used to be a ubiquitous metal spatula design, but I can never find them anymore. I've found it is much better to use something small like a cake / bar server than something big like a grilling spatula.
Don't cook on cold cast iron. The trick my mom showed me is you always wait until a splash of water (get your fingers wet and flick it on the pan) will start boiling on contact. If it boils into nothing immediately, you are too hot. If it just sits there and does nothing, you aren't hot enough yet.