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Make sure you have your Google business listing set up (and bing places for business)

Put your address in the footer of your website and use schema markup

https://schema.org/address

This will associate our business with your area.

Here's a handy article

http://www.thesempost.com/google-using-near-keywords-search-results/

and another

https://clutch.co/seo-firms/resources/9-steps-to-rank-for-near-me-searches

I've never implemented this but......

Schema does offer this

https://schema.org/parentOrganization

and also this

https://schema.org/branchOf

So you would set up the branches of your organisation with different addresses.