Do you have any photo editing program on your computer? If so, what do you use.
Alternatively, if you have MS Office, with Powerpoint, (or Impress from OpenOffice/LibreOffice). I find it is very easy to resize images in that, more so than Word or equivalent. As your picture will be behind glass-type protection, the image will appear glossy anyway.
Alternatively, hang on until someone can give you more detailed help.