If You’re new to ACF & PHP – it’s easy.
Step 1:
Make ACF field: image and set “Return Format” option to “Image URL”
Step 2:
Let’s say You give the Label “My background” -> the (autogenerated) Name will be: my_background so:
Now You can use it anywhere in post / page:
<div style="background-image: url(<?php echo get_field('my_background'));">...</div>
