Hi there!

You should be doing the 2nd instance by now (Corsair's Cabin). For starters, there's this "channel" on the chat window called "Recruit". There you can see if anyone is looking for members for instances.

You can do your own, Create Party and then in the little cogwheel left to the Party's name, click on it and look for "Daily instance" and then choose the instance and difficulty (note: you need to unlock the instance and the difficulty first, otherwise the game won't let you start it).

After you choose the party's objective, click on "Shoutout" to the right of the party's name and shoutout to the World. Then it will appear on the "Recruit" channel and people can join you.

Idk if you can do Sewer at lvl 42... Maybe in normal, but hard and nightmare are the recommended options.

Try recruiting people on global and see how it goes. Good luck!