Your best bet would be to start on the OverDrive site which can be found in All Digital Resources located under Find It on the main library website. Once you get to the OverDrive site you can click Collections and then look for Audiobooks. You will have the option to click Available Now for titles that are currently checked in or See All for everything that the library owns.
Digital titles also appear in the regular library catalog but it is much easier to search using the Overdrive site.
Overdrive Digital Materials
In the Libby app you can set your preferences so that you only receive audiobooks in your search results. Here is a link for how to change preferences - Setting preferences to filter your library's catalog
