I’d like to be more constructive, but Anoon is right. Your question could be distilled to "how do you plan, what are all the tools". It’s a bit too big a question tbh, a bit like going on a car enthusiast’s site and asking "how do I fix engines?"

Don’t be discouraged though, you’re entering a whole new world!

Look though this forum, there are a couple of threads where people recommend books on planning procedures. Get a recommended one that relates to whatever corner of industry you’ll be planning in and read it. There is also a page of links to internet based resources, much of it free.. Also, try to find an experienced mentor, they are worth their weight in gold.