Hi! 

There are differences between some offices and firms, but generally HR is there to help and ready to hop on a call with you and clarify things. It helps to be nice and build a relationship with them because then they will be extra generous with the information they provide. LinkedIn is a good way in, otherwise if they have an official contact that also works. They are usually reluctant to put you in contact directly with a consultant, but once you pass the screening most office provide mock interviewing support with some of the local consultants. That's a good opportunity to ask questions. 

So bottom line is, ask. The likelihood is very high that they'll answer and you'll get to learn about the application process.