Resizing for a new format

[Andi]

I work at a church. I design the graphic for our web banner first, but then I need to change to the size for different formats, such as, facebook, church bulletins, and the sanctuary screen. I keep searching for a simple way to change it. I duplicate the original, and have tried changing it through image size and canvas size, and nothing seems to work. So I far I have had to redo everything from scratch. I know there is a simpler way. Please help!

[st3f]

Canvas size changes the size of the drawing area without rescaling the image that is contained within it.
Image size rescales the Image that you have drawn.
It sounds like you're trying to do the right thing.
Can you post any images showing what is going wrong?