Are you even understanding what we are telling you?
You MUST plug your monitor into one of the video card outputs. If the cable on your monitor is different, and won't work on ANY of the outputs from your graphics card, then you will need to either get an adapter that will allow it to be plugged into it or use a different input style from your monitor if is has multiple input options. If it does not, you might need a different monitor in order to use that GPU card, although there are usually at least one type of adapter that can be used to adapt, for example, VGA to DVI-I or something similar.
Looks like most of the RX 560s only have DVI, HDMI and Displayport outputs, so you'll most likely need an adapter of some kind if your monitor only has VGA inputs on it. You can check the monitor to see if there are other inputs beside where the VGA cable runs to that can be used. That will require you to get a different cable if it does.
You also might need to plug in an extra power cable from the PSU to the graphics card, if your monitor does have one of those three inputs but it still does not work when trying to use them. Knowing exactly what the model numbers, EXACTLY, are for your monitor and graphics card would go a long way towards helping you figure out your problem, but you will never be able to use the graphics card by plugging your monitor into the motherboard. Cannot, and will not, ever happen.