These things are long understood, may I humbly suggest a library and not an internet forum for your answers.
Whilst I am here, you say you understand how evolution can be involved in human traits that we see. I assume you don't know how these traits are produced from your question or your assumption that intelligence is required.
The DNA is copied millions of times a second inside a living organism. It makes millions of mistakes All the time in copying. Some get through the dna 'spell checker' some dont. Errors made in the DNA can lead to anything from cancer, to being covered in hair, to having 6 fingers to having all the organs in your body on the wrong side of the body. Or indeed a freckle. It can also lead to skin pigmentation changes, patterns etc etc etc.
These errors in the DNA only offer the traits , it is the enviroment that selects them, hence the term 'natural selection'. There is no intelligence involved at all. Let me explain....
Let's use a real example : The Peppered Moth.
Before the industrial revolution moths were prevelantly white in colour. Why? Because that made them camoflauged to the ash trees they sat on, and difficult for the predators to see. The industrial revolution brought smoke and dirt, the white moths sat upon darkened trees were now sticking out like the proverbial thumb of soreness. Black moths now survived and reproduced in larger numbers in an enviroment where smoke made surfaces a lot darker.
So the dna mutations gives us the various colours and patterns in the moth, the enviroment and predatorial behaviour dictates what is advantageous And what is not. Survival of the fittest is the most misunderstoof element to evolution in my experience, it is not the strongest, fastest, most vicious... darwin CLEARLY explained that it was a refferal to the enviroment. Whichever organism fits the enviroment best, will procreate more, it is common sense. These organisms will orevail and so will their genes.
Try
not to get hung up on the specifics of this example, it is a real example and very useful for explaining the mechanism of mutation and then natural selection. Use it to understand the role of the genes and the very seperate role of the enviroment. That is all evolution is.
Do you have anything to ask following this? P.s. a good book is 'The Greatest Show on Earth' by Dawkins, or a great textbook is 'Biology' by campbell and Reece. Dawkins explains it in very simple terms with lots of examples, but has an atheist pov, the textbook is a little more hard work but aimed at a 16yr old so not too bad.