How to adjust DPI of photos?

I'm in yearbook, using the eDesign program. My partner had to use an iphone to take pictures of a wrestling match for our page. I want to use some of the pictures, but edesign won't let me. When put on the page, it says there's an issue with the DPI. I just don't understand how iphone photos can look high res on the phone, and print to high res 8X10 photos, but have an issue with the DPI when made into a 1 inch size picture. Is there any way to fix the DPI of the images so that I can use them?

In a photo editor like Photoshop (or even a free one like http://www.Irfranview.com ), open a copy of your original image. Click on resize. Set it to the width in pixels or inches you want it to be, then set the dpi to at least 240 (I use 300), then save your image with a new name as a medium compression JPG. You may need to tick the 'constrain proportions' (or similar box) to prevent a cropped photo from being squashed. You may wish to apply sharpening. It will now print nicely.

When you report an error message, quote it rather than paraphrase it in general terms like "an issue with DPI"

The funny thing is DPI is a printer setting, not a photo setting. It is fully independent of the the pixels per inch. For a lot of photos, 72-150 pixels per inch is plenty. This might be printed at 2400 or more DPI (partly because the millions of colors are made up of droplets from 3-12+ tanks)

You do not state how you get from full size down to 1", use photo editing software to do this in a "re-size canvas" or similar menu function, don't just grab the corners and shrink it. Also mind the format, make sure it is a standard format that your design software can use.

You can try using this to resize, change DPI and print.

http://keerok-photography.blogspot.com/2012/09/software-for-resizing-changing-dpi-and.html