Guild Wars 2

OK I guess I am dense to already be lvl 60 and only now ask this question. But…. how do I use the upgrades most effectively. For instance, you have upgrades (Like upgrade for Miladru etc)that give you something like 4 different skills, it kind of says 1. Power
2., 3 and 4
i.e. for everything a different skill.

So how are you supposed to stack all four into the weapon/armor.
I tried to put a second one onto an armor and all it did was overwrite the previous one even though it also was Melandru. So how do you stack?
For each one it says click twice and put on item but that is evidently not the case!

You must put the same kind of rune on multiple pieces of armor, not on the same piece of armor.

Ohhhhhhhh thanks for ther reply. I used to play this game ages ago and only just came back. I remember now. Takes a while to get into it all again, but I am determined to now get from 60 to 80 despite there apparently not being a huge amount of people playing it any longer, but still, there seem to be enough fans around still.