That means you can vote at work, school or any other convenient place, and you can find your polling place at the city's Board of Elections and Ethics site.
For the council, I suggest you vote for Patrick Mara to get a different voice out there. (And even if you don't support Mara, these Mara-memes are pretty funny.)
As for budget autonomy, I didn't write about that before because it's pretty obvious that yes, you should support DC's budget autonomy. The basic idea is that it will give DC more autonomy with its own budget -- right now Congress is able to approve or deny various parts of it. In the past, for example, Congress stopped DC's ability to implement a medical marijuana law that passed in 2002 and also cut funding for abortions.
But as for the referendum today, it's unclear what actually will happen, but to me it's a good start. Even if Congress tries to challenge it or somebody takes it to court, it might result in more visibility for our plight as a district without a vote in Congress and a voice in our own affairs. Maybe one of these days.