Hi Steve,
You should be able to post links in the description of your image, though unfortunately the software doesn’t automatically spot web addresses and turn them into hyperlinks currently.
When editing your observation, you just need to select the text of the web address, and then click on the “link” item in the formatting toolbar above the description editor (the icon on the far right which looks like a pair of handcuffs). A pop-up window will then invite you to enter the URL you want your text to link to.
Best wishes,
Dominic