How to reset wrench symbol? 2013 CX-9

Normally I would suggest checking your Owner's Manual, but I checked for myself and found that the process is not listed in it.

A quick Google search turned up this Reddit thread, where a Mazda tech mentions that your Malfunction Warning Light is a non emissions related fault code that requires an OBD2 device to pull and clear the code. Try visiting an auto shop like NAPA or PartSource to see if they can clear the code for you for free.