At the beginning of the post or page, use the Text editor to add this above all of the other HTML:
This creates an invisible target at the top of your post or page which hastopas its ID. It can be helpful to have an invisible target if you don’t actually want to add visible text to the location of the target.
Alternatively, instead of putting the ID attribute on an empty<div>tag to create an invisible target, you can add the ID to the first element on the page – such as a heading – like this:
<h1 id="top">Page Heading</h1>
You can use the insert/edit link button to link existing text to this target by putting#topin the URL field, or you can write this in the Text editor: