ive been playing ac4 but i want to complete all challenges which require these events, problem is, nothings showing up. all i have is a royal convoy icon which leads to nothing.

Can someone help?

i'm not entirely sure but i believe that the community events are both triggered by ubisoft and by friends online. lets say someone finds a chest or a white whale, it will let your friends know where they are and they will be able to have access to it. Again i'm not 100% sure and if anything you can google it.