If you have an Amiga 500 Plus, then you have the ECS and should be able to connect it using a simple VGA adapter. However games and demos won't work on the VGA monitor. (Haven't tried this myself on the A500 Plus).
If you don't have the Amiga 500 Plus you will have the OCS chipset and won't be able to connect it to an VGA monitor at all, if not buying a Scan Doubler (expensive). But then also games and demos will work on the VGA monitor.
Otherwise you should look for a RGB cable to use instead of the A520, it will give a bit better picture on the TV set than the A520.
