These are the steps, simplified.

1. Secure a location. In most places, owner permission is sufficient to locate on private property; however, there are exceptions (notably, HOAs). Do what diligence you must to feel great about proceeding.
   Privately-owned, publicly-operated properties (businesses, schools, churches, nonprofits) can help avoid privacy/traffic concerns as well as red tape accompanying a city property location. If allowed at all, projects on city property are always more labor and time intensive. (The tradeoff is good community buy-in prior to launch.) Think of several potential host sites, and go with the most enthusiastic. The project host is a critical partner. 

2. Make a mini pantry. There are no organizational requirements re: design, but offer your host design input. Build or purchase a box, repurpose furniture, use an old newspaper vending box. Call your project whatever you would like. 

3. Talk about your mini pantry. Consider creating a dedicated social media account to communicate about your mini pantry. This will stoke interest. Once folks start shopping, you probably won't be able to keep your mini pantry full. DON'T TRY TO! A sometimes empty mini is an important control at the site that keeps stewards from policing behaviors and those shopping from loitering, etc.,(not to mention you'll wear yourself out trying to keep a small box full in a high need environment). What you can do is enough.

4. Don’t over-complicate. At first, there's a lot you won't know about your mini pantry. Learn from it before adding salt!