The wallet directory is located in:

/Users/[USERNAME]/Library/Application Support/Syscoin

Note: the Library directory is hidden by default, you can quickly access this directory by pressing:
CMD + Shift + G
in Finder then typing:
~/Library/Application Support/Syscoin

/Users/[USERNAME]/Library/Application Support/Syscoin/wallet.dat is your actual wallet file. 

On Blockmarket 1.00 be sure to back it up regularly as sending and receiving Syscoin often creates new address that may not be included in an old backup.

Syscoin 2.2 and up (the core of BlockMarket Web) use a single address.