Everyone begins with the same default PIN, "changeme", and the user ID is your library card number including the "D" and any zeros, but no spaces. To change your PIN, log on to the catalog with the default PIN and go to "My Account" at the top of the page. There you'll see an option to change your PIN (make sure you write it down if you change it!).
Note that if you log in before you begin searching the catalog, you will not have to re-enter your User ID and password each time you want to place a hold; the system will supply them for you and direct your hold to your home branch. See Catalog.