To create a new partner (a company, customer, supplier, ...) or to display the list of existing customers, use the menu Sales > Customers. This menu does not only allow you to create a new partner, but also to search for partners.

Click the Create button to add a new partner. Tick the Is a Company? checkbox to indicate that the new customer is a company and not a private person. You will notice that a new tab page Contacts is added in front of Internal Notes.

You should at least enter the company's Name in the partner form. Some fields are text fields, other fields may be linked to existing data that have been entered elsewhere, such as Countries. 

On creation of a new customer from this menu, the Customer checkbox is automatically ticked. Why is it important for you to correctly set the Customer and Supplier checkboxes in the partner form? These checkboxes are designed to enable Odoo to quickly select the partners who should be displayed in some drop-down boxes. An example: when you select a partner in a Sales Quotation, Odoo will only allow you to select from the list of Customers. And that is precisely what the Customer checkbox is used for.

To add extra contacts, or add s specific address type, such as an invoice address, follow the next steps. Go to the menu Settings > Configuration > Sales and tick the option Allow a different address for delivery and invoicing.

Click the Create button on the Contacts tab page (for an existing customer, make sure you click Edit first). Now type the name of your contact and fill the other data as required.

To specify an address that is different from the company address, untick the Use Company Address box. Now select the appropriate Address Type. You can choose amongst: 

• Contact: address of the contact person
• Invoice: specific address for sending invoices
• Shipping: specific address for sending delivery notes
• Other: any kind of address
• Default (never to be used, because it will be the company address).