Navigate to UW procurement website (https://f2.washington.edu/fm/ps/) and click on Eprocurement icon: 
Login using your UWNetID and UW password.
In the top main menu, click on ‘Search->Catalog’:
Search page for the vendor you will purchase your item/s from (alternatively click on ‘Catalog’ dropdown menu)
Next, click on the ‘Buy from Supplier’ button.
The supplier’s page will load in browser page lower frame (notice Ariba frame persists on top of web page):
Add item/s to cart.
When you have added all items from supplier, you need to complete purchase by completing order. This part varies per supplier as each supplier web page is different. For McMaster-Carr for example, I would click on ‘Current Order’ link. For other suppliers, it may be ‘View Cart’ or similar.
Finally complete order in supplier frame.
This final step will close the supplier web frame and TRANSFER your cart/purchase to ARIBA Eprocurement requisition.
Once the cart has been transferred, you will be in the ARIBA requisition page. There are three steps that must be completed on this page.
(1) Enter descriptive title.
(2) Check the all items checkbox. (only if a single budget/project number will apply to all items)
(3) Click Edit button to edit all line items.
Once you click edit, you are will be in the line-item edit page. In this page, you need to add:
(1) Budget number. Note this is not a simple text field. You must look up the budget number by clicking the down arrow and then by searching for your budget number.
(2) Add project number. Append XXX to end of project number as in 'L04XXX'
(3) Click
The next page will allow you to review changes you made to line items. If everything looks correct, click button.
FINALLY - to complete the purchase click button.
All Done, put your feet up and congratulate yourself for using ARIBA Eprocurement to create requisition.