I also work in Big 4 but I started in September last year. It seems that you are a new hire based on you stating that you took off the fall to work on the CPA (congrats on passing it!). The person above me made some great points that you should take note of! But I also want to point out some stuff that you should also take note of that people won't put to you straight. I wouldn't necessarily tell people that I delayed my hiring to take the CPA. Yes this is your first job, but taking off to take the exam is generally frowned upon in my B4 firm in NYC. There are certain people (not myself obviously) that may resent that, people who have not finished but took the traditional rout of starting in September. Be careful with how you frame why you started later.
Now on to more important things, you are slightly behind your peers as most have done a Q and/or interim by this point and will be a little more fluid with the audit/tax software and in general the environment of corporate america. Also, coming from a staff perspective, on the job training in B4 can really go either way, so as the previous poster said, take notes when you ask questions.
If you interned, connect with your friends from your internship (fellow interns and former seniors/staff) and definitely network with your starting class. They will be an important support system for you during busy season, also they will be good to have if you have questions about your typical first year stuff (sample size calc, workpaper templates, etc).
Your first two weeks will probably be training but the second you get your laptop and get booted up, reach out to the engagement senior and introduce yourself, tell them you're excited, ask what you will be working, ask for the understanding the entity work paper to familiarize yourself with your client and ask if there are things you can get while you're in the home office for them. You can even go the extra mile and ask if they need you to do anything! (Hint hint, ask for access to the EMS file, or if in AS2, as for the PY backup).
Make contact with your counselor and your OBA also.
In short, get excited, get ready, and bust you a** off because to show that you can compete with your peers!
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