You have been recently send off, by your chapter, to join Deathwatch; this is an honor you were chosen for since you were a scout (Neophytes, in the case of Black Templars) because of your exceptional skills and potential.
As of now, you are on board an imperial strike cruiser, the Vigilo Oculus, on route to your first mission in the The Jericho Reach’s. It will take you about one month (warp time) to get to the xeno Warp Gate, the Well of Night.
You have not been introduced to your inquisitorial handler, the other members of your kill-team, or briefed on the up coming mission. There is only a few members of the Adeptus Astartes on board, however, so they are easy to track them down if you wish.
All you brought with you was your weapons, armor, and a serf provided to you by your chapter. Though they do not know it, but after your tour with Deathwatch (or your death, which is more likely) they will be mind wiped and turned into a servitor so they can serve your chapter even in death.