converting HTML to wp PHP

I am very new to wordpress and I am trying to convert a basic html layout to a wordpress site. I have followed many books and forums and still running into certain issues.
– none of my images are loading
– the title of my post most recent post loads followed by- Fatal error: Call to undefined function the_post_thumbnail() in /home/content/41/7378741/html/scottsword/wp-content/themes/scottsword/index.php on line 15
– my footer only loads when you click on my post but my post doesnt load.

I don’t know if I need to add more php code or where. If anyone could point me in the right direction I would REALLY appreciate it! My site is https://www.scottsword.com if you want to look at the actual problem.

Thanks All!