Didn't Study Finance in College - How do I prepare for my job?

For those of you who graduated with degrees in Econ, History, Stat, etc., what did you do to best prepare for jobs in IBD (assuming you didn't intern in banking the summer before)? Having virtually no classroom experience with Accounting and limited working knowledge of excel, it's hard to not feel like I'm at a disadvantage compared to my peers who will have studied Finance/Accounting in undergrad business schools.

The obvious next steps are to practice excel and read up prior to starting full time - but I'd like to know how some of you guys with Liberal Arts degrees found yourselves acclimating to your careers in finance and what you did to specifically to catch up to your peers who came in technically superior. I figure a lot of stuff will be covered in training but recommendations on books, courses, other resources would be greatly appreciated.

TLDR; degree in underwater basket weaving but will be working in IBD, how do I avoid being shitty at my job