How do I go about getting an upgrade of a zero percent service-connected status?

I'm a gulf war combat veteran who served 9 years in the US Army (8 active, 1 in the CA National Guard). When I DEROS'd in 1997 from active duty at Ft. Lewis, WA...I was blessed to take part in an active attempt by the Army to true-up military medical records and automatically apply for service connected disability benefits (even though the two areas I was eligible for service connection were at zero percent). I'm pushing 50 now and both areas where I'm service connected are getting worse with age. I've also got CPTSD (diagnosed by the VA). How can I go about (e.g. what's the process) for getting the two areas where I have zero disability already evaluated for upgraded as well as adding my CPTSD and having a determination of service connection and a percentage allocated? In a nutshell, how would I go about getting (and whom would I contact to get) an updated evaluation? Is there a process that anyone else has followed that worked? Any assistance with this would be very helpful. Thanks in advance.