You've played pen-and-paper role-playing games, and now, you fancy yourself a pen-and-paper game master (or called a "dungeon master" in D&D)... but you don't know what to do?
Step 1. Go get advice. You can search easily enough and I recommend it, but here's one. It's brief, though. I recommend looking for additional info. We have some DMs among the community, too. Go full on zombie and pick some brains.
Step 2. Try out the advice. Everyone's gotta start somewhere, and it's best to not just fumble around completely in the dark.
Step 3. Tweak your style. Learn. Gotta break some omelettes to make some eggs... or something. Keep at it.
Step 4. Profit. Enjoy.
Simple? Maybe. Keep at it, and it will be.
Worth it? Yup.