Can I just go poloniex exchanger and purchase 10000 SJCX to join Test Group B?
If yes, what is the process after purchased 10000 SJCX?
Test Group A and B are exclusive to our crowdsale supporters. So even if you buy 10,000 SJCX you won't be able to participate unless you have an SJCX crowdsale address.
You will have to wait for Test Group C to be able to join the beta, more info here:
http://storj.io/earlyaccess.