First Alert(ed)

 I have a new First Alert Smoke & Carbon Monoxide Detector, with 10-Year Alarm Life. I opened the package, and tried to figure out how to activate it. Instructions on the back of the unit on "How to Activate Alarm" read:
(1) Align alarm with bracket and turn sideways. (Ok, this connects it to mounting plate.)
(2) Press and hold test button to ensure alarm is activated. (There is a rectangular disc on the front.  Pressing it did nothing. And, unlike the others we've had, there is no other rounded button on front.)
The only other instructions printed on the back reads "How to Deactivate Alarm." I veer away from this because once the unit is deactivated, it is dead, and must be replaced.
    Finally, after searching for answers, I called Customer Service. The solution is simple. The tab by the Deactivate instructions, with a single downward-pointing black arrow, must be moved, not downward, but upward. Wouldn't you think they'd offer a clue?    It can't be me. It's them!