EOS Rebel T7 How to take photos at 300 dpi

[Redsed]

I am just learning how to take photos of my artwork to post on a marketing site. I am told I have to post a min. 300 DPI photo which means I need to change my settings and photograph all my artwork...again.  Can someone give me a simplified explanation about how to do that. Sorry if this sounds a little crazy but I have put myself in a position to learn every. single. thing. about websites and social media and cameras all at once.  If I can just take the right pictures I will be miles ahead of where I am now. There are plenty of tutorials about what to put the setting on when you start out but not what any of those settings actually mean.  Thank you so much for any information. 

[johnrmoyer]

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@Redsed wrote:

But how do I set my camera to get that resolution? They want me to have every photo at 300dpi to be able tto print several different sizes of prints. 

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Since your camera produces an image that is 6000x4000 pixels, if you are able to exactly use all of that resolution then you could sell a print up to 20 inches by 13.3 inches at 300 dpi. If you want to sell a larger print, then you could use a program such as hugin to stitch together several photos as if you were making a panorama.

I guess that the 300dpi might be a minimum and that the marketing company will scale the image before printing it because it does not make sense to me that they would want you to upload a separate image file for each print size. But, if you have a 6000x4000 photo and want to sell a 10 inch by 6.67 inch print by uploading exactly 300 dpi you might use the free to download Canon Digital Photo Professional software to save at any resolution you might wish, in this case 3000x2000 pixels. Canon Digital Photo Professional would also be willing to put the 300dpi number into the meta data when saving. In Canon Digital Professional one can set the units for resize to "inch" along with 300dpi and the software will do the arithmetic for you.