Where do I see "soft sleeper options" for the rail from Beijing to Harbin?

1. "Soft sleeper" options for rail including fare and schedule -- where do I find this information?
2. When is online booking made available? Have checked a number of sites, but I only find booking made available for tickets up till end Sep? So if I want to purchase tickets in time for Harbin ice festival, when should be the best time to do so before it gets sold out?