I read a few sites, http://decompose.co and how to compost and a few other sites
is it really that complicated?
Is there anything else I need to learn?
To add to stormy's answer, the reason some information looks "complicated" is that there are basically two ways plant material can decompose, and you need to make sure your compost heap uses the "right" one and not the other.
Actually, so far as recycling the nutrients is concerned, it doesn't really matter which happens, but the "wrong" one gives you a slimy wet evil-smelling pile of gunk, not dry crumbly odorless material that is nice to work with.
The difference is which bacteria are doing the decomposing. Some are "anaerobic" i.e. they don't need any air to do their thing, and they produce a cold, wet, smelly mess. The ones you want are the "aerobic" bacteria. They generate a lot of heat as a by-product of the decomposition process, which keeps the compost dry. If a compost heap is "working" really well, you can literally see steam rising from it in cold weather. The temperature inside the heap can get as high as 50 or 60 degrees C (120 to 150 degrees F).
To keep the aerobic guys happy, the basic things you need to do are make sure air can get through the whole compost heap (i.e. don't pack the material too tight) and make sure the bugs have the right nutrients (i.e. add nitrogen if necessary). Otherwise, the anerobic guys will win.
The advice about "mixing greens and browns" is basically to make sure the air can get in - the "brown" material doesn't pack down so tightly as "green" (think bits of twiggy wood, compared with grass clippings).
Turning over the material is basically to make sure everything gets composted. The center of the heap will naturally be hotter than the outside, so you want to mix up the material periodically to make sure all of it gets some time in the center of the heap.
The other main issue is making sure you don't set up a luxury centrally heated hotel for rodents - i.e. you need something to contain the heap and keep them out of it!
Composting is not complicated at all. Composting is 'enhancing' a very natural and normal event on our planet. Something that lived, dies, and IMMEDIATELY starts decomposing. Even us humans.
Composting kitchen and yard scraps in one spot makes a better compost as well as speeds up the decomposition process. We humans live on a different time scale than other life forms.
There are a few 'flavors' of scraps; primarily green and brown. Green is mushy, wet...brown is airy, crunchy. Never use any poo poo or meat or dairy or as I've just learned potatoes in your compost pile.
Compost needs air, heat, nitrogen to aerobically decompose. The decomposition process causes heat as a by product of decomposition. Until that matter that was once alive and now dead is completely decomposed it is useless to the soil organisms or any other garden process. The decomposers, however get first dibs on any nitrogen inherent in the now dead organic matter. Keeping amounts a reasonable size so that you can easily go out and turn the whole mess with a pitch fork and/or adding nitrogen to feed the decomposers hastens the process. Alfalfa pellets that they use for kitty litter or rabbit food are ideal. Simple nitrogen to feed those decomposers working hard decomposing.
Once organic matter once alive and now dead is completely decomposed that matter is now available to all the soil organisms. That is what the life in the soil needs to eat for energy. Critical stuff. This compost in no way should be considered fertilizer for plants or ever used as soil for plants.
When the process is done, the material looks nor smells at all like the original material. Looks like yummy soil but it is not. Taupe, fine and even textured. If you can recognize any material that compost is not finished.
Put on top of weeds, raw soil and around your plants...not too close to woody stems and trunks.
The life in the soil goes up to the surface, eats this decomposed organic matter, goes back into the soil, poops all the goodies out mixing organic matter into the soil better than the gardener could or should. Inhibits weed seeds, smothers established weeds (depending on depth) and feeds the life in the soil. No plant could complain as long as there was correct watering, just enough ADDED balanced fertilizer and drainage. Compost decomposed is Gold.