1st make sure the practice has an attorney, if they don't you could private contract with one. You do NOT want to negotiate contracts/fees without an experienced contract attorney unless you have done this for a while.
2nd, find a course to take if you don't have time to self - study and learn. I have done credentialing for years before I ventured into contract and fee schedule's negotiations, I also took college courses in contract law and obtained my paralegal. There are even small things you pick up such as what to do if the carrier tells you they don't negotiate (many will tell you that), just from experience doing it. There are also formula's and data gathering you will need to do and very strict guidelines about discussing fees with other providers. (some will try to do this to see if they can get same rate and it puts both providers at risk)
It's really not as easy as just jumping into it, What I did when I started was I stuck with the carrier negotiations and then let the attorney sign off and review..If I used MY attorney they would bill the client and I would bill for my work, the lawyer just becomes a private contract.