Find and click on the establishment that needs a new service provider.
Under "Actions" Select "Edit"
Find the field that says "Provider" and begin typing the name of the service provider that you would like to link to this establishment. Once it appears in the drop down menu, select that provider and click the green save button at the bottom to save the provider.
(Note: if they are self-cleaner, just search "self" and select self cleaner)
The selected provider will now appear on the establishment's page, and on their online profile.