How to mask in CS2?

[Harlequin]

Just got myself a full version of CS2 to use in conjunction with PSP... I have a mask layer on one of my psp files but can't get PS to recognise the layer. I go to layer mask, and try hide all or reveal all but nothing seems to enable me to mask the whole image. I can use a mask on an individual layer but how do I mask an entire image? I want the layer itself to act as the mask, not create a new mask layer and then edit that. Is this even possible?

Thanks in advance.

H

[Harlequin]

Nevermind I found the alpha channels window... and the help files