In you haven't already, you need to create a profile. Go to google.com/business. Follow the step-by-step instructions to create you account.
Step 2: Fill in Every Detail of Your Business as Possible
Don't miss anything! Include your company description, hours etc. There is a large place to elaborate on the details of your products and services. You can create product/service categories, add images for each offering, and even add a link to the relevant page on your website that discusses each service.
Step 3: Create Posts & Upload Images Regularly
Posting regular content on your profile, as well uploading photos of any events etc helps your GMB profile. It allows for customers to see and understand your business; this helps but a face to the name of the company. It also prompts Google to show your business as opposed to a competitors when someone searches for your services. Google likes to show businesses with fresh content.
Step 4: Update Your Profile Regularly
Updating your profile shows Google that you are "on top of it", and you have not simply created your profile, and have abandon it. They see regular updates as a more reliable source of information. Filling in holiday hours as they come up, confirming or denying suggestions made by Google help them understand the information on the profile is correct.
Step 5: Get Reviews & Respond to Reviews
Lots of high-rating (ideally 5-Stars only) reviews on your GMB profile not only look great to potential prospects, but is a major factor chosen by Google when they decide which business they want to rank, when users search for services you provide in your area. Don't be afraid to ask your customers for reviews. Don't forget, as you acquire reviews, respond to them! Google likes to see a reciprocal relationship between a business and their customers.