Hi Michael, I think Mike captured it well, but to build off what he said. You will likely receive training once you join the firm. One of the biggest thing you can do now is work on your learning how to learn. When you start a new job, a lot of things will be new (and this can be overwhelming, it certainly was for me), so it is important that you know how to process and retain the new information that you will be receiving.
It's been my experience that companies will provide training on the specific job functions you will perform in an internship. Important skills to have are active listening, engagement, MS Office (or equivalent) proficiency, etc. A lot of these skills can be found on sites such as LinkedIn Learning, Udacity, etc. If you want to work beyond that you might look at any classes that support coding, accounting, engineering fundamentals, etc. You can always inquire on what department or departments the PwC internship would be supporting and see what skills you may need to support that department or departments.