If that's the first mission, they spoon feed the UI to you piece by piece as a tutorial. Would have been nice if they told you!

Just keep doing what your told and on the first real mission it will "all" be there.
Also, your left wondering what to do in the pen at that point. You can't board the boat so head further into the pen till you get the two characters that highlight. The first guy lets you load your eels, and the second gives you your mission. When in that map, you select the mission at the top left box that you may need to open with the orange arrow. Close the map, talk to the same guy and select the start dialog. You'll see.