How can you figure out prerequisites you need? Look at your project plan. What steps are you planning to do? For each step, consider what skills and resources you need to accomplish it. Don't rely on getting lucky. Be reasonable.
For example, if a step is to build a log cabin, you should know how to do that. That means e.g. knowing cabin design and some woodworking skills. You'll also want a chainsaw and nearby trees. If a step is to trap wild animals and sell the furs, you should know what sort of traps to use, what animals are in the area, how to set the traps up, how often to check them, etc. If your plan is to spread ideas, you should know what the ideas say and why, why the ideas are superior to alternative ideas, and the answers to attempted criticisms of the ideas you're spreading.
What if you plan to learn as you go along? Knowing how to set a trap is a prerequisite for setting a trap. But you could do it in an earlier project step instead of before the project starts. That's often unwise because learning doesn't always go smoothly and it's hard to plan projects based around skills you don't yet understand (will you even like doing it?). Anyway, putting prerequisites earlier in the same project doesn't invalidate the concept of prerequisites.
It's also possible to divide a step into sub-steps and mix in learning prerequisites. You can split building a cabin into 20 steps, then watch a YouTube tutorial about the first of those steps, then do it, then watch a YouTube tutorial about the second of those steps, then do it, and so on. This is generally only a good idea with pretty simple, easy projects where success isn't very hard to come by and delays aren't a big deal (it especially works well with practice projects where learning is the main goal).