09CTS4AWD- While I agree with everyone on here that you should not disconnect your battery for no reason at all; you did ask how to disconnect your battery. This forum is about asking and answering questions and helping others. You did not ask "Should I disconnect my battery?"
So, here's what you do with that black "tab". Lift up and swing it to the right (while lifting it up). When this tab is loosened, you should be able to just slide the connector off the terminal. You should not need to apply excessive force at all. If so, then consult your dealer.
Don't let everyone scare you into not disconnecting your battery if you need to. When/if you do disconnect your battery, be sure to read your owner's manual for instructions how to properly connect your battery and reset everything. It's really not that scary; if it was truly dangerous, the battery would be inaccessible. Just use common sense and follow the owner's manual; it's there for a reason!
