Novice Player and Baby DM with Newbies

I am a new player. I am still playing my first campaign that I joined part way through, and we have only even spent time in a small village for a small time, and the rest of the time has been in the wilderness. I do have the benefit of listening to D&D podcasts for a couple of years. My players though have had little to no exposure (my two brothers and whoever else we rope in).

I have a really fun idea to introduce new players to how DnD works and helping them become comfortable with their character, but once again I am so new. Any advice would be fantastic, especially on how to run a campaign in a city type environment (I'm starting them off in a forest to reduce complications at the beginning) with all the complexities and choices involved in that kind of environment.

I'm stubborn and want to write a campaign for my brothers instead of relying on a premade campaign. Please and thank you in advance.