To "screw up ___" means to make a mistake. It's a phrasal verb that can work like this:
I screwed up the recipe and it ended up way too dry.
Or like this:
I screwed it up.
You can also use "screw up" by itself like this:
He just won’t admit he screwed up.
A similar phrase is “mess (something) up,” which has the same meaning but is a little bit more polite.