Add New User; Admin on Team Account No Longer with us

Our previous admin on our team account, Matt Ivey, hasn't been with us for a few years now. We have a new hire and trying to get her set with with her own box account under our team. My boss can access Matt's email address, but all the billing is still going to him as well and we want to get that switched over as well to myself or a new team member. 

Can you please assist?