how do i edit saved layers?

[PhotoshopFreshman]

im new so....anyways.k.i made a painting and saved it as a photoshop file.it saved my layers settings.then. i opened my painting to continue where i left off.when i tried erasing something in one of the layers i saved it in,it wouldnt let me.it wouldnt even let me edit it or anything.plz help.

 

[iDad]

probably bottom layer .right click it....>remove back ground does that help?

 

[iDad]

or check >image >mode

 

[hawkeye]

What do mean it wouldn't let you? Explain what happens when you try to erase. Are you getting a pop-up message telling you the layer locked?