Point your browser
here. You'll see this:

You can click on "Choose Photo/Video" if you already have the image file somewhere on your computer (
supported file types), or you can paste in an image url from the web, or if you have taken a screen grab and done a "copy" you can just press Ctrl-V to do a "paste".
Wait until you see the "Upload Completed" notification (1), hover over the image and click on the menu (three dots) next to "Copy" (2), then click on "Get Share Links" (3).

Click the "Copy Link" button for "
BBCode (Forums)".

That will put a text string similar to the following on the clipboard, except there will be no extra spaces between the square brackets:
[ img ]https://i.imgur.com/K3AMPuA.gif[ /img ]
Paste (Ctrl-V) that text string, as-is, into your eHam post.
To add another image click outside the "Share Options" sub-window then scroll down a bit to see the "+ Add Image" button.

Click that button and repeat the above steps.
When you are done composing your post you may want to click the eHam "Preview" button to make sure everything looks good.

For example, in this post I wanted to show this:

That animated gif is part of the
Seeing the Effects of Local Terrain on Radiation Patterns thread over on QRZ.com.
Dan, AC6LA
https://ac6la.com/