I'm still @#%$^! cause I can't do this from my OneDrive account... 
I don't have a OneDrive account, but it works a lot like Google Drive, if I recall correctly.
Try these steps to share one image:
(This guide is assuming that the images are already uploaded into your OneDrive account, and you're trying to share an image from your account.)
1. Pick the image you want to share by selecting the circle in the upper-right corner of the item.
2. Tap or click "Share" on the bar at the top of the page.
3. Under the "Share" options, you have two to choose from: "Invite people" or "Get a link."
4. Since you want to share the image on the forums (where anyone can access it), click on "Get a link."
5. Then, click on "View only." (You don't want anyone with the image link to be able to edit it, so ignore the "Edit" option.)
6. Select "Create link."
7. Copy the link ("URL") address. (Use the buttons Ctrl+C or right click and select "Copy" or "Copy link.")
8. When you're posting the image on the forum, use the image tags around image URL address that you just copied.
Paste the image URL address in-between the image tags:
[ img]image URL address goes here[/ img]
9. Remove the spaces in front of "img" in the tags so that it will show up properly as an image in your post.
You can also shorten the link after Step #6 (click on "Shorten link") and then copy that URL address. Paste the shortened URL address in-between the image tags, as shown in Step #8.
Hope that helps! (Note that I'm doing this from memory... ^__^")