Following a tutorial done in 2.78 on the anvil, The next step was to add a ref background. The environmental node went through a math node to background node but I don't know what to connect it to in 2.93.Could you please tell me where I have gone wrong this my best attempt, but no picture, behind anvil and no world lighting in viewport.
Click on the left center of your screen where it says "Object" and change it to "World". You will then have access to to the World Shader options (Including the Background Node). Make sure you are in Rendered Preview Mode in order to be able to see your image and have its lighting influence your scene. Or, if you want to stay in Material Preview mode, enable "Scene Lights" and "Scene World" from the Viewport Shading options menu (arrow next to the preview mode circles - top right):