please use any graphic software (like gimp, photoshop, corel) - fill whole template with images & keep all the important elements inside violet areas. there are 2 templates - one for front & back and another, almost identical - for inner left and inner right side. dotted lines are approx. cutting lines & there is about 10mm of safe margin (inside & outside dotted line = the gray area) - it means image can shift in the process by max of 10mm in&out of each side - that’s why its not possible to put anything important (like text) on a spine, and also that’s why you need to fill it out with image/background too (if there's any). center of the inner side (spine back side) will not be printed (see example photo below), avoid any "line"-like borders, it will look odd when there some misalignment happens. i made it a bit transparent to show fitting to template below:

(we show only one part of gatefold, but preparing inner left/inner right part it's about the same)

and here's how it should look after your art is done - with no template elements visible. just plain, print-ready graphic ("what you see is what you get!"). best results would be RGB image with 300-600dpi resolution, good quality JPG or TIFF/BMP (our template JPG file has those parameters set already). if you still dont how how to make it, send square images for the front and back cover, we will try to make it printable

common mistakes (click to enlarge):

background not stretched to fill margins and a spine
(if there's misalignment involved in the process it will result some white margins here and there)

important elements (texts) too close to cutting line

template left on the final image (all that you see will print)