SOLO is the libraries' online catalogue. You can find maps here as well as books, journals and other materials. If you are just looking for maps it's easiest to use the Map Search.
The Map search can be accessed here, or by following the link from SOLO front page.
A simple search here will just find maps:
There's also an Advanced Search for maps; click here or follow the link from the Map Search page. You might find this useful if you're not finding what you want with a simple search. See the next page of this guide for more detailed guidance.
If you haven't used SOLO before, you may find it helpful to consult the general SOLO guide first.