Schema Premium plugin has support for schema.org Service type that allows you to add schema markups to pages about products on your site.
Follow these steps to add the new markup type:
1- Create a new Schema markup
The very first step is to go to Schema > Types, and click on the Add New button.
2- Select schema.org Service
The next screen will open the quick schema.org creation wizard. Select the schema.org Service type from the drop down list.
When you are done selecting; Schema Premium will confirm the creation of the new schema.org type, and you will have the choice to go through next steps, which is configuring the schema.org type you’ve selected.
3- Configure schema.org Service
Create a set of rules to determine the target locations of this schema.org type. For example, you can enable this markup on a specific page or post, or you may have a custom post type for pages about Services that you would like to enable this type to work on.
3-B- Product Properties
Optionally; this section allows you to configure schema:Service properties.
4- Update Schema
Click on the Update button to update schema.org type.
5- Test Structured Data
Test your schema.org markup in Google’s Structured Data Testing Tool to make sure it’s valid. You can test your markup with a simple click.
Here is an article that explains how you can test your schema.