Sharing Imgur Pictures - Quick PC version
Not getting into how to use Imgur, or navigate that service. But once you have a picture uploaded - here's what you do.
Click your image, which takes you to the pictured screen. Then hit the Copy button for "BBCode (message boards & forums)":
Guests cannot see images in the messages. Please register at the forum by clicking here to see images.
Go to your forum post and paste the link where you want it. If the picture is too large for the post, easiest thing to do is modify the link using the Resize Imgur Pictures Shares guide.
That's about it!
Update Feb 4, 2020: Per Jefferz post, you don't even need an Imgur account to do this. But haven't done so personally.