Hi mholden,
By default, the Vendors tab is located in the QuickBooks tab group. You can find the QuickBooks tab group by hovering your cursor over the current tab group (this is to the left of your username in the top right hand corner of the screen) and selecting QuickBooks from the dropdown menu.
If you would like to be able to access the Vendors tab along side your other tabs in the CRM tab group, you can add it under Customize -> Tab Groups. I hope this helps.
-Audisho