Manure heap is a kind of U shaped wall structure object where animal manure appears when this placeable object is put close enough to cattle, cows or pigs barns.
FS22 does not give any indication at the build mode if manure heap will connect to any animal barns/sheds if placed at the current spot, you just have to judge by eye from experience, then once placed walk up to manure heap and see its info box if it shows connection.
On internet there was some "non working manure heap, use manure heap extension instead" info floating around, its some old outdated data on stupid frigging youtube videos from conzole peasants, in FS22 v1.12 there is no problem using "manure heap" next to cow / pig barns. Never watch youtube video guides they are a complete waste of time as most of the time they get outdated very fast, so always rely on up to date web pages with text.