Steps:
First you need to create an account at: https://bitshares.openledger.info/?r=sinto2
Then go to https://openledger.io/market/ZAPPL_OPEN.SBD and deposit SBD:
You can buy SBD on Polo: https://poloniex.com/exchange#btc_sbd
Go to balances: https://poloniex.com/balances and search for SBD.
For adress just type: openledger
For memo: just copy the whole memo line from the openledger
Back to https://openledger.io/market/ZAPPL_OPEN.SBD and just execute a buy order :)