The VXA has a blade-brake clutch (called Roto-Stop). Be sure you "let go" of ALL the levers, controls, etc. first. Next, just hold on to the main handlebar, and pull the starter rope. This will get turn the engine (and start it). The blades remain stopped. After the engine has started and warmed a bit, you must (1) Push the wide black blade control lever fully against the handlebar and hold it there (2) Press down the yellow blade lever until you hear it click and the blades start to spin. Release the yellow lever. When you want the blades to stop. release the black lever; the engine will keep running until you move the throttle lever to OFF.
Read all about in the owner's manual.
(1) Have the serial number off the back of the mower deck ("MZCG-1234567")
(2) go to this page, and scroll down the the "HRR216VXA" section. Click on the link under DOWNLOAD that's in the range for your serial number: