Tree Tutorials [Propositional, Predicate, Identity, and Modal Logic Trees—Howson Syntax]
This section of the tutorials and
Colin Howson,  Logic with trees ISBN: 0-415-13341-6
would work well together.
You need to know some propositional logic to be able to understand the tutorials to come. In particular, you need to know about the symbols used in propositional logic, truth tables, satisfiability, consistency, and semantic invalidity (by counter example). You do not need to know propositional rules of inference and derivations.
Howson  will give you enough background.
Alternatively you could look at the first five propositional tutorials in Easy Deriver