The page you’re linking to has to have named anchors.
In this case, the section of the page linked to is named “Semantic_pleonasm” and is designated with the hash mark #.
In the case of Wikipedia, it’s easy to pick up the anchor names by using the menu at the top of the page to navigate to the section you want to link to. That will automatically load the full URL into your address box.
If the page you’re linking to doesn’t have named sections, you’re sunk.