Photoshop layers question

Hi,
I'm shooting sunsets. It's difficult to get a good exposure for sky and foreground in a single exposure. I can take two exposures - a good sky exp.and a good foregroundexp. I wish to experiment blending them in Photoshop CS.
How do I open one image file -edit to opacity etc. reqired and then open the other file, do the same and then blend or rasterise/multiply the two files to make the one multi-layered image.
Do I have the concept right and can it be done?
Any tips most gratefully accepted (by hopeless image twiddler)
Cheers,
I'm shooting sunsets. It's difficult to get a good exposure for sky and foreground in a single exposure. I can take two exposures - a good sky exp.and a good foregroundexp. I wish to experiment blending them in Photoshop CS.
How do I open one image file -edit to opacity etc. reqired and then open the other file, do the same and then blend or rasterise/multiply the two files to make the one multi-layered image.
Do I have the concept right and can it be done?
Any tips most gratefully accepted (by hopeless image twiddler)
Cheers,