During the day following the Joining, the newly made Wardens and their companions will be called in for group mission briefings, either informed of it by the senior Wardens themselves or told to come to a room by a messenger/servant. This isn't going to be happening ICly, but you are welcome to mention these sessions. It would be unwise for the Warden-Commander to send in their troops unprepared and unaware of what they could be facing. For example, they know at least a little about broodmothers -- they'll be told what signs to look for, strategies to kill one, etc. Same goes for Deep Roads. The group with presumably the least amount to learn is the one headed to the Brecilian, but even then, they'll be describing the basics of how to identify different types of darkspawn, since the Forest will likely be one of the first places to be corrupted if the horde is moving northeast.