I guess its the same way as you did for SCJP. Buy the voucher from the place where you purchased the voucher for SCJP and then prepare for SCBCD referring a book and long time buddies for java the ranchers. For SCBCD, you need to know EJB 3.0 . Well i have just started to learn EJB using EJB 3.0 in Action.
[ SCJP 6.0 - 90% ] , JSP, Servlets and Learning EJB.
Try out the programs using a TextEditor. Textpad - Java 6 api