First you need to figure out who you want your customers to be.
If your answer is local coffee shop owners, then it's easy to make a list of customers and you can call them, email them, or visit them in person.
There are many places on the internet that give free advice on how to do cold calls, emails, visits, etc. Steli Efti writes about it a lot on the close.io blog. There are numerous questions asked and answered on quora.
Start at those two places and once you know more of the basics, you can start learning more specific skills.
But if you don't know who to talk to, then you are trying to solve two problems at the same time: who to talk to and how to talk to them.
Solve one problem first, then the other.
Once you know who to talk to, then you can start talking to them to see if they have the problem that you are trying to solve.
If the service or product you are selling doesn't solve their problem you are not going to be able to sell it to them.
It's much, much easier if you are trying to sell to a customer base (market) that you understand well or already know some problems they face.
Then you can talk to them and verify that you are correct and they have the problem that you think they have.