How do I remove a background? A client had send me a full colour jpeg and I need to create a cookie cutter from the image
You would need to do this in some other software. The easiest is probably to google for background removal websites that will provide tools to do it. There are quite a number of free tools these days, some will let you select areas to delete - some will attempt to automatically detect the background.
If you want to do it manually you can use free software like gimp/getpaint.net/krita and use tools like magic select to delete the parts that you dont need.