Adding Multiple Locations for a Contact in the Web Portal can be done from the Contacts List view, the Locations List view, or from the full Contact page view
To add a new Location via the Contacts or Locations list views, go to CRM > Contacts > choose either the Contacts or Locations list > Click on the Contact/Billing Name > select Location > + symbol, and then add the new location details and Save.
To change it via the full contact page, CRM > Contacts > Select the Contact ID or Arrow in the list > Locations > + symbol, then add the new location details and Save.
To add multiple location on the App > Contact > Select the client you would like to add the Location to, Locations > Select drop down box > +Add New Location.
This can also be done when creating a job.