You will see an image link at the bottom of each post on this board leading to GCS.
Members can't change this as it is set in their profile and posts, just as the PM and Email links are.
To do this.........
Users & Groups - Profiles - Contact Field tab - Click to create a new field.
Add the name and the image url
Necessarily filled ? = Yes
Display = Messages and Profile
Display Type = Text
Who can modify = Moderators
Then scroll to the bottom and in the next box fields........
Choose Web Address
Add the url to the link you wish the button to go to.
Save
Then - Click the black button at the very bottom