Making kettle corn is actually pretty easy. It is made in a single pot on the stovetop and typically only takes a few minutes to finish. You can add as much or as little sugar to the mix as you want, depending on the overall sweetness that you are going for.
When choosing an oil for popping, be sure to look for one that can handle high heat since the oil needs to be extremely hot to pop the kernels. Coconut oil or palm oil are both great choices. Alternatively, you can also go with canola oil since it has a relatively high smoke point and probably won't burn. Avoid olive oil, however, since it has one of the lowest smoke points of all cooking oils.  Here's what you'll need to get started: 
- 1/4 cup vegetable oil (coconut, palm, or canola oil are preferred)
- 1/4 cup sugar (more or less depending on how sweet you want the kettle corn)
- 1/2 cup unpopped popcorn kernels
- Salt to taste
- Large saucepan with lid
- Baking sheet with parchment paper (optional)
Add the oil to the saucepan along with two or three popcorn kernels. Cover the pan and put it on the stovetop over medium-high heat. Once you hear the kernels pop, you know that the oil is hot enough. Remove the lid and add the sugar and remaining popcorn kernels. Put the lid back on the pot and start shaking it back and forth as the popcorn pops. The shaking helps keep the sugar from burning. Continue shaking until the popping starts to slow down. It is best to err on the side of caution and remove it right when you notice the popping slowing rather than waiting too long. Otherwise, you will wind up with burnt popcorn.
Once it is done, remove the lid and immediately pour it out on the baking sheet. While it is still warm and sticky, salt it to taste. After it cools, transfer it to a bowl and enjoy!
If you prefer, you can also make a lighter version in the microwave using nothing but a paper bag, some sugar, oil, and unpopped popcorn kernels. Here's a video that shows how (just be sure to skip the staples since putting metal in your microwave is never a good idea)