You don't. Dots per inch (DPI) is irrelevant to the camera, and it sets it to 72 only because it needs to set it to something. DPI is only relevant when printing. You can set it indirectly by choosing the size of the print, or you can set it directly and let that control the size of the print. Either way, it's up to whatever program you use for printing, not the camera that shoots the picture.
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You don't. Dots per inch (DPI) is irrelevant to the camera, and it sets it to 72 only because it needs to set it to something. DPI is only relevant when printing. You can set it indirectly by choosing the size of the print, or you can set it directly and let that control the size of the print. Either way, it's up to whatever program you use for printing, not the camera that shoots the picture.