You should be getting an in-game notification after doing group content saying "give accolade." You press X and you get a list of the players you just grouped with and pressing X over their names gives you a choice of the type you want to give.

If you're not getting a notification then I'm not sure there's another way, tho tbh I haven't actually gone out of my way to look for one.

You can only give accolades to people who aren't on your friends list tho, so if you're playing with friends you won't get a notification.