How to add social media icons and when we click on it , it should direct to a particular page?
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You can search for the desired icon on your web browser and copy the image address in source parameter of a!webImage or you can download that image and save it as a document inside Appian folder and use the constant to point the document in a!documentImage. And for directing to a particular page, you will see a link parameter where you can use a!safeLink to pass the URI of the page you want to open.
Yes, as mentioned above you can download images/icons as document then you can use it to be clickable.
It's not readily available, but it can be built easily as other members suggested.