Inquiry on how to make a character move

I am attempting to develop a game where a diver enters a sea and gets a treasure, but one of the obstacles im facing is how to animate the diver once the player hits the movement key as if the diver is walking and i also dont know how to animate it’s legs as it’s only a png.

That’s a bigger and much more vague question than maybe you realize. First, I assume you’re using 2D since you mentioned a PNG. You’ll either have to animate that yourself using something like Photoshop or better yet Aesprite, find someone willing to do it, or leave it as is and work around it for now. Second, movement is already fairly predefined in Unity, but perspective matters a lot. Is this top down? Is it side scrolling? That all changes movement a good bit because you have to modify rigidbody settings to work with the gravity. I would recommend doing a few of the official tutorials until you get the hang of some of it, and if you don’t know C#, I would actually start by learning the fundamentals there, separately.