Samsung Health challenges on iPhone

Having trouble with rubbing damaging health on my iPhone. Is there a way of setting up challenges on Samsung health on my iPhone? All I was able to do was join a global challenge but I was unable to challenge any of my friends. Also, my friends were able to add me as a friend but get a message saying that I don’t accept challenges. How can I set up the Samsung app so that I’m able to use it? It’s really easy on an android device but the Samsung app seems limited in terms of functionality and user interface seems a lot less robust than in an android