Can you please explain the process of buying a train ticket?

I am travelling around China and need to sort out my Visa. I understand that I can buy my tickets up to 60 days in advance - can I buy them now for April? (I know this is more than 60 days) How does the process work in terms of picking up the train tickets for verification at the station, as my first ticket will be from shenzen to Guilin (from Hong Kong). What is the process once I have bought of this site please? Thanks