Engine knocking

Is this rod problem.Can it be fix thru the valve covers?

If this is genuinely a problem of “rod knock”, the bottom end of the engine has to be opened up in order to get to the crankshaft. Additionally, if the rod bearings are shot, the main bearings are probably also badly worn, and there may be other issues that will need attention, such as the piston rings. All of this requires that the engine be torn down.

What make, model, year, engine option, mileage? What does the knocking sound like and how fast is it knocking at idle?

IF it is a rod knock, then NO, it cannot be fixed through the valve covers. By the time you hear the knocking, the rod is toast, and must be replaced. This can only be done by a near-complete disassembly of the entire engine.