Are you looking to purchase from the discount employee purchase program (DESPP)? If so, you have to go to BNY Mellon to do that. From what others say, do it soon because it looks as though there will be a quiet period soon when you won't be able to do anything until 12-Jan.
To get to the BNY Mellon site from UPSers.com, go to the My Life and Career Tab and then click on the Mellon Investor Services link on the left hand side.