Well, that's a good start

Current word count: 0

I know what I'm going to write about, and have a setting and a few characters and a genre (dieselpunk whodunnit set on an airship). 

I don't know who actually dun it, why they dun it, or who they dun it to. 

I'm sure it will become obvious at some point.  First of all I need to get a bunch of characters onto the airship.  Then I need to work out who most wants to kill someone else, why and how.

And stop being distracted.