You can easily create a vendor while editing an invoice or doing it by clicking on the "Vendors" tab in Invoicing.
Vendor URL Image corresponds to the logo you want to add at a vendor, it will appear on the invoice. URL corresponds to the URL of the website of the vendor or his compagny. If you activated Community Builder, the "First Address", "Other Address", "City", "State", "ZIP Code" and "Country" will be saved on Community Builder and the lisy of Countries will the the Community Builder's. You can add "Addition Notes" but they won't appear on invoices, order or quotes concerned by the vendor.
Some fields are required, you can see which ones by clicking on save if you didn't fill them they gonna be followed by "Fied is required". We added three check for the field "URL", "Phone" and "Mailing address". If you start to begin them you have to respect the way URL, Phone or a mailing address look like otherwise you won't be able to save it. It prevents from doing typo by writing some vital data from your vendor.