Custom POST API Call

Hi
I’m new to this forum & Camunda, so my question may have been asked in previous forum questions…in which case i apologize…

I want to trigger Camunda process using a customized API call and would like to know how/where i can start doing this… the following is an example of the type of API call that i would like the Post API to look like:

  POST /product/car
  {
     "name": "order Products",

  "description": "ordering new car",
  "productSpecificition": {
      "id" : "1000",
      "name": "BMW320",
      "version": "2018"
   }
  {
	"variables": {
    	"color" : {
        	"value": "Green",
    	    "type": "String"
    	},
    	"engineCapacity" : {
        	"value": "2000cc",
    	    "type": "String"
    	}
  }
}