First step is to choose which Group you'll want to post your picture in. At the top of DU's home page is a box for "Forums & Groups. I usually post in Photography, sometimes in "Pets."
Next step is to join an online photo sharing site. I prefer Imgur. You have to create an account with which to sign in; however, the service costs nothing. (Although it tempts you to sign up for the "Ads-Free" feature at $5/month. Ads-Free is not necessary.)
Once Imgur is on your screen, click "New post" in the green box at upper left. A box will appear offering three different ways to upload your image. I use the option at the upper right: "Choose Photo/Video" and click on it. (I select my pictures from the desktop.) Click on the image and click on Choose at bottom right of the box.
Once your photo is in the Imgur box, RIGHT-CLICK anywhere on the photo. A box of choices will come up click on Copy Image Address. (You need not "Give your post a title" on Imgur, because you'll be posting on DU.)
Back to the DU groups page youll see a blue box Start a discussion.
Click on that box and youll see a box for Thread title and another for Message text. Give your photo a title, then in the Message text box, RIGHT CLICK to post the photo from Imgur.
WHEN YOU RIGHT CLICK, IF THE WORD "blob" followed by a long string of numbers and letters appears, delete the string, go back to your picture in Imgur and repeat the process Copy Image Address again until you get a much shorter string that begins with "https" and ends with "jpg." Usually takes me 2-4 tries to get the correct string.
Back on the DU group page, click on Post my thread! at the bottom of the page. Your image should appear on its own page.
My final step then is to return to Imgur and at bottom right click on Delete post. Close Imgur. Of course you could save it and/or post it on Imgur all I do is upload and delete.
To post more than one photo, just click the box
+ Add image.
Any questions, or screw-ups on my part, please send me a DU mail message. Thanks!