I am new to dreamweaver. How do I centralise a heading and image?

Horizontal & vertical centering with CSS flexbox.

https://jsfiddle.net/NancyO/pqhoc5r3/5/

Horizontal & vertical centering with CSS Grids

https://jsfiddle.net/NancyO/9jtfvd5k/

Post back if you have more questions.

There are a number of ways to centre align elements, all using CSS properties.

• text-align: center; - https://www.w3schools.com/tags/tag_center.asp
• align-self: centre; - https://www.w3schools.com/cssref/css3_pr_align-self.asp
• align-items: centre; - https://www.w3schools.com/cssref/css3_pr_align-items.asp
• align-content; - https://www.w3schools.com/cssref/css3_pr_align-content.asp
• margin: auto; - https://www.w3schools.com/howto/howto_css_image_center.asp

and none of these are the responsibility of Dreamweaver; they are what you should know when using Dreamweaver.

I have a feeling that you would benefit from following thus tutorial: https://www.w3schools.com/bootstrap4/default.asp