How do I add a video, image or link to an item description or Info Page?

In items, edit the relevant item, then in the description box click either the video icon, image icon or the chain icon (link).
To input a video click the video icon and enter the video's url and click save, as shown below.

To add an image click the image icon.

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Then click and search for the file you would like to add or drag it in to the box displayed.

To add a link to your text, highlight the text you would like to link.

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Once highlighted click the link icon and paste your link in the display box and select save.

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This process also works for info pages to do this go to Setup > Info Pages add or edit an Info page to show the edit box.
Follow the same processes as shown above.