Creating a Property Database

I developed my company’s online company portal (much like an intranet) and need to create additional database(s) called: properties, vendors, and clients. Each group will have their own sub categories (eg. “Properties” will have “Property Name”, “Address” , Client Name <= which will be tied to the “Clients” database so this item would be selected via drop down or combobox and this box would have all the Client names from the client database. I would also need the ability to add new entries from the admin panel. How do I create an additional database(s) for these items.