Download the PDF, print the combinatorics section, grab a red pen, and prepare to get stuck. Because getting stuck is where the learning begins.

"Don't look at the solution until you have spent at least two weeks on a problem." — Arthur Engel (paraphrased)

The beauty of having Engel in is that you can annotate, search for keywords (like "pigeonhole" or "coloring proof"), and jump between the problem set and the solution appendix instantly.