Every time I save the image to my laptop, when I go to open it, the file says "we cannot open this file"
Image files need to be associated with a program to open them. You can usually drag the image onto your web browser to open.
What format are you saving? In LunaPic, File -> Save it will give you multiple types. Choose the right image type for the image you're saving. Do not right click on image in lunapic for save options.