You will find Ask the Librarian chat at the bottom of this page - see yellow button (shown in the image below).
On other library pages the chat may be displayed running down the right hand-side of the page (as below).
If there is no librarian online at any given time you will have the option of searching our FAQs or submitting a question through the form on the right hand-side of this page https://lit.libanswers.com/