GOG is suppose to contact contest prize winners via the forum's instant messaging. I don't see a IM link anywhere on the GOG website. How do winners claim their prize? Some help is much appreciated.

Put your mouse over my avatar next to this post and notice the Start conversation option.

Your privacy settings look okay since I can message you, but you may want to review them just to familiarize yourself with them.

Edit: I didn't notice this is a duplicate of
https://www.gog.com/forum/general/gog_forum_instant_messaging_service_question