Click on the blue button marked "New" in the upper right-hand corner.
Fill out all the fields on the "Create organization" form, making sure to fill out the required fields marked with a red asterisk.
Click the "Vendor" checkbox to denote the organization as a vendor.
When finished, click "Save & close" button in the lower right-hand corner. (Note: the button will be grayed out until you begin typing in the form, at which point it will turn blue.)
The new Organization record you just created should appear in the third column on the screen.