- How are City and Office related?
- Is City a custom post type with a many-to-many relationship, or is it a custom field within Office? If so, what type of custom field? What is the field slug?
- What type of search are your clients using? Is this a WordPress search, or a Views text search, or a custom field filter?
Install the plugin and follow the instructions to enable custom fields in your search results. Note that only some types of custom fields are compatible. Let me know if you have further questions after following the instructions in the guide.