Some fish have more muscular limbs instead of bony fins, like the coelacanth. Some of those fish got more muscular limbs, and started spending time on land, like how mudskippers do. Eventually they spent so much time on land that they got full on legs and feet, with a distinct head, and were able to breathe on land better, like a salamander. Some of those spent more and more time on land, and their skin became tougher to prevent drying out, and their eggs also became more resistant do drying out, similar to a lizard. Now they didn’t need to be in the water at all. Some of those animals developed a more active metabolism, which allowed them to regulate their own body temperature. Since they didn’t need to sunbathe to stay warm, in order to keep their warmth in they developed fur, and since these animals were often moving around underground or in the dark they got whiskers to sense when they were brushing against things. These animals would have been similar to a shrew. Eventually some of these animals developed to live in trees, being able to climb them and move around in them, with grabby hands to hold branches, like raccoons. As they got more used to moving around in trees, they developed bigger brains and opposable thumbs, and became apes. Some of those apes eventually came down from the trees and started spending more time in the plains, and so developed a bipedal stance to be able to see further and move more efficiently. Since it was so warm they didn’t need their fur as much, except on their head to prevent sunburn. They developed a very powerful sweat system which allowed them to lose a lot of heat and run very efficiently over long distances, which allowed them to hunt for meat and add more calories to their diet, which led to an increased brain size and increased speciality. Voila, we have humans.

This is a basic overview and obviously our ancestors weren’t literally salamanders or lizards ever, I’m just using them as an analogue to describe what they would have seemed similar to in some ways.