Colin Howson,  Logic with trees Chapter 2
Howson  has a number of exercises. Many of them you will be able to do in the Widget below.
You can also try material of your own.
Here are a few hints
- You have to use the right (unicode/html) logical symbols. Check Writing symbols
- The symbols in use here are ¬ ∧ ∨ → ↔ (so copy and paste or drag and drop these).
- When entering from a selection, the software will take a single formula (say, A) or a comma separated list of formulas (say, A,B,C) or a possibly empty comma separated list of formulas followed by ∴ and another formula (say, A,B,C ∴ D). In the last case it will load the negation of the conclusion.
- Just type, cut and paste, or drag and drop, whatever you wish, into the lower text box. Then make a selection and hit the Start from Selection button.
Exercise: Roll your own