How can i start a MCJROTC program at my local high school?

can you ? nope

can the school ? yes, but it takes a couple of years

they have to find both a retired officer and a retired SNCO to teach the program

plus find the space for the program

IE: a space to store the uniforms, weapons you march with, etc

You can't. Only the local school board can decide that. The USMC JROTC program is a real niche program and lacks broad appeal. Even if you got board approval, the USMC might decline the invitation due to what they consider limited potential.