Finally, a question I can answer! I found this link and was able to add my custom header on my blog https://www.youareoncrack.com successfully.
https://www.blackbam.at/blackbams-blog/2012/06/25/custom-header-images-plugin-for-wordpress/
When using this code don’t forget to add the php tags before and after which are <? … ?>
To center my header I just added standard HTML tags <center> … </center> and it worked.
My only issue now is that my theme is responsive but the header image is not shrinking for mobile and tablet resolutions which is what I am trying to figure out now.
Hope that helps, at least it displays correctly on all computers.