How would I fit a decomposer on a food web?

[Babyjustrun]

I've been looking for hours to figure out how to stick a stupid mushroom or something in.
I know that they eat dead vegetation or animals, but can I put it in without putting 'dead vegetation' as one of my organsims? If that makes sense at all?
Some of my animals do eat mushrooms, etc...
But I'm not sure how to draw this.
We spent more time with food chains than webs that I'm just so confused on it.

-sighs-

Thanks in advance.