The pictures were taken from my phone, so I apologize if the quality is not good...
HKIA has two "arrival halls" labeled A and B, however both halls exit into the same arrival floor... The path to the lounge is at the exit exactly in the middle of both arrival halls. If you exit out of "A" go right and if you exit out of "B" go left.
This is the view of Arrival Hall "B" from the middle of the arrivals floor
Look for this sign in the middle of the arrivals hall... Look for the "pay shower" icon on the bottom right of this sign [this is coming from arrival hall B].
Follow the sign and you will see this sign with "Pay-in/Shower Lounges". That is the only "sign" that directs us to the lounge. Keep walking straight ahead...
You will reach this "intersection" follow the "Terminal 2" Sign and go down the escalators.
When you reach the bottom of the escalators you will see the Plaza Premium Lounge to your left, just keep walking straight past that lounge.
After passing the Men's and handicapped's washrooms, the Arrivals lounge is on your right, just before the green emergency evacuation sign.
Hope this helps!