Preparation for Externship at a Credit-Focused HF?

I'm a second-year undergraduate student, and this winter break I will be participating in an externship opportunity at a credit-focused hedge fund/asset manager. The issue is that I have a very limited amount of knowledge regarding the types of securities they are trading and their business in general. Up until now, I've been an equities guy so this is super foreign to me, especially the lending side of their partnership. If anyone could steer me in the right direction in terms of what to read to better prepare myself for the experience I would greatly appreciate the help!

Here is a brief description of the HF: The firm is a credit-focused asset manager that offers a commingled hedge fund, co-investment vehicles and customized solutions to its LPs. The fund invests in residential and commercial mortgage-related instruments and consumer-linked structured products.