when you sign up for your UPS account here:
register
you set the user ID and password for your account. Use the User ID you enter here for the account, and use the password.
after creating the basic account, you need to obtain an account number which is used as the shipper number:
exp_pdf2.html?srch_pos=3&srch_phr=UPS+Account+Number
when you obtain the account number for billing purposes, you will also be sent an xml key.