How to Change Image Resolution with go pro?

[Carlo]

Goodmorning,

does anyone know how could i change the image resolution of photos before Shuttersnitch export them in dropbox?
I only found how to resize them.

This images are shot with GoPro HERO3+ Silver.
I need to print them on 6x4 photographic paper (on the same paper i usually print image with 1920x1280 of resolution), but right now they do not fit the paper.

Thanks,
Carlo