As explained when image hosting was introduced:
adding a picture to a question or answer is now as easy as …
Clicking the Insert Image toolbar button
Selecting an image from your computer, or the web
After that, replace the default "enter image description here" with something meaningful for browsers that do not support images.
Even when selecting "from the web", the image will be copied to the Stack Exchange Imgur account, and hence will be safe from expiring.
If you just want a link to an image:
- Use the steps above
- Remove the leading exclamation point from the result:
[click for my image]
If you really want to hardlink images from another source, without copying them to the Stack Exchange Imgur account:
- Use the link tool to make a regular link to the image
- Prepend the link with an exclamation point:
Bear in mind that:
To make it easier to find relevant information using search engines, be sure to copy important text into your post too. (Messages from popup dialogs can often simply be copied using Ctrl-C or Command-C.)
For the screen readers of visually impaired, for browsers that don't show images, for cases where Imgur is blocked, and for search engine indexes: please enter a good description.
Whenever possible, use the Stack Exchange provided hosting as described above. This uses an imgur.com Pro account, which ensures images are never lost. Images on free Imgur accounts, and on many other free image hosters, will expire if not requested every now and then. The post should be useful for future visitors too.