Hi Mary
Somewhere on the software program that's creating the image, there should be a function, usually under the edit menu, that says image size.
This allows you to make it bigger or smaller. If you want to know how big the image is now, it's 94 x 29 pixels. (Right click the image.. then click propertiesd, that tells you the size.)
My siggy is 200 pixels high x 946 pixels wide. That's probably as wide as you'd need without distortion.
Also by changing the size on the menu, you can keep the right proportion.. and stop the image getting distorted, which it sometimes does if you change size by dragging it.
Hope that helps Mary. What software are you using to make the image?