Oh I may have misunderstood what you wanted.
If you have two layers on one Picture. Meaning you had the original and then copy and pasted another layer on the original.
Choose the layer you wish to work with by selecting it on the tool bar, usually on the lower left hand side of the screen under the layer tab.
THEN
Goto the top tool bar on the screen and select the Layer link.
When you get the drop down menu choose Layer Style
Then slide over and take Blending Options.
This will open a window with the tools.
You will notice a slide bar called Opacity.
You can slide that bar left or right to make the layer show up less or more.
There is also a box you can check under the new style button to give you the preview of the image so you can see how transparent you want the image.
Hope that helps.
