A few of the services require only that you enter their sites from one of our library's web pages.
Most ask for your library card number. This can be right up front, or very subtle.
To use the Consumer Reports widget, put your search term in the widget box, that then takes you to the screen where you enter your library card number.
Userful asks for both your library card number and PIN. You will also need both when you log in to your actual library account.
A small number of services ask you to set up a personal account. These tend to be ones where you would want your place saved - tests, lesson sequences, or books that can be read/listened to online or downloaded. These are also likely to have mobile apps available. They retain a link between your account and your library card number.