There are several ways you can interact with your connections:
Send a message - You can send a message to any connection. They will get it in their inbox.
Add to list - Add a connection to a list and keep them organized.
Send business introduction - Introduce your business to any connection and start your commercial relationship.
Ask for a quote - Ask a connection to send you a quote for a product or service.
Ask for a review - Ask a connection to review your business.
To be able to perform any of these interactions, you must select (this icon represents the action central for any connection/contact). This will show the menu where you'll see every action available for other businesses.