The Circuit Design Space software should have a Page Setup option that lets you scale the output image to take up the maximum area on the page, as well as position it (top, center, etc.).
Are you aware that the maximum image size that Cricut Design Space can print through the Safari interface is 6.5 inches by 8 inches? If you are unable to resize via the menus, how about the following:
1. Print out the image in whatever size
2. Cut the paper with a scissors so that the image is as far to the upper left (the "northwest") corner of the page as possible.
3. Scan the image
4. Use any graphic software that you have handy (Paint, PaintShopPro, PhotoShop) to scale the image up by whatever factor you desire.
5. Print the scaled-up image.
6. Use the magnified image so produced to drive your Cricut cutting machine.