Read the guide first before starting the plan - specifically the recomposition and nutrition sections.
The 4-week plan was designed to work alongside the guide's principles so the two complement each other directly. The plan tells you what to do in the gym. The guide tells you why, and how to eat to make it work.
Starting the plan without reading the guide first means you'll be following sessions without understanding the reasoning behind the structure. You'll get some benefit but you'll miss a lot.
Read guide first, then start Week 1 of the plan. That's the intended order.