how to layer

I am currently trying to do basic layering functions in photoshop 6.01 with windows xp and do not understand after reading help and experimentation how to view basic layering effects or how to achieve them. I went from photoshop 4.0 to 6.01. I use to do a large number of images and layers to do complex photographic collages. I need a basic explanation of how to view and vary layer opaqueness, how to copy between layers, etc.

you need to read the FAQ first, then post in the "New to photoshop help" because this is a question for newbies not advanced PS users, and then maybe ask nicely...

I'll post it in the correct area.