In what order can i add multiple tangs?

[OrionN]

To OP,
If the above, your picture, is the Yellow tang you are talking about, then you don't have a "Yellow Tang" but likely a Mimic tang according to your picture. He looks small. I would add a small Sailfin or Scopa next, then PBT last, or else you can add all at the same time. If you are going to add a Blue Tang instead of PBT, then add him first, or all at the same time.

Of the 5 fishes you mention the aggressive order is:
Blue<Mimic<Scopa=Sailfin<<Powder Blue. BPT is very agreesive but he is also very beautiful. Add him small and last and he, and the other tangs should do fine.

Another reefer advise that PBT should be biggest so that he does not feel threaten by the other tangs.

.....a larger pbt might be too large to feel threatened by a smaller yellow and aggression might be minimal.....

This is absolutely wrong. In a new group of tangs with PBT being the largest, you will have dead tangs.