Some total newbie advice needed again....:redface: How do I fill the layer black, then merge the two layers together...
Press D key on your keyboard. This will reset your foreground and background colors to black and white.
If the black square is on bottom, press the X key on your keyboard, this will reverse the order.
Next, choose your Paint bucket Tool.
Click once on the empty layer in your workspance/document (not on the layer in the layers panel) and this will fill layer with black.
As this should be in it's own document, there is no need to merge the layers together. Just save as whatever file you need..........jpg, .png, etc.