How can you integrate your customers with your FB page in terms of retail services?

You can run a marketing campaign with loading your data base in it, then all your customer who uses their numbers or emails in FB will get to see your page. 

Or, run a promo discount offer for customers to like your page.

You can print out fliers or stickers displaying your Facebook page requesting them to like it and give them to your clients or still you can create a database for your clients and try to link up with them via your Facebook page

keep customers engaged with new products and the latest promo's, and it would be great if you launched prize's promotion which people love the most. and always show them the added value and the best use of your products