OK, there are so many problems here.

1) vars is a pointer to a buffer.
2) series() returns a pointer to an array created by Zorro.
3) vars MyGlobalArray[1]; creates an array of one pointer (which defeats the purpose of it being an array).
4) the manual was hinting at using an array of var (that is, doubles), not vars (pointers to doubles). And once you do, you have absolutely no reason to call series because you supplied an array.

OK, now try this. (Not tested, I don't have time):
Code
function run(){
	if(!Test){return quit("!Click [Test] to begin");}
	assetList("AssetsFix");
	asset("EUR/USD");
	vars MySeriesArrayX = series(0,-5); 
	vars MySeriesArrayY = series(0,-5); 
	if (!Init){
		int x;
		for(x=0; x<5; x++) {
			MySeriesArrayX[x] = 20220101+x;
			MySeriesArrayY[x] = x+0.1;
		}
		
		int date;
		for(x=0; x<5; x++){		
			date = MySeriesArrayX[x];
			printf("\n date: %d",date);
			printf("\n number: %f",MySeriesArrayY[x]);
			
		}
		return quit("!Done!");
	}
}