chesky Check the site section by apps and read how to do it.
Btw you need to have internet on the phone.
"Voice Access - Control your phone using your voice
Voice access allows you to control your phone entirely with your voice, including apps that do not support a flip phones keypad.
After installation, voice access requires the following commands to get it working
First run adb shell to get you into a on device terminal.
Head over to WebADB and follow the instructions to connect your device. Then go to the Interactive Shell section.
Then run the following commands in order
am startservice com.android.cts.apps.accessibility.voiceaccess/com.google.android.apps.accessibility.voiceaccess.JustSpeakService
settings put secure enabled_accessibility_services com.android.cts.apps.accessibility.voiceaccess/com.google.android.apps.accessibility.voiceaccess.JustSpeakService
settings put secure accessibility_enabled 1
pm uninstall -k --user 0 com.lge.voicecommand
If you get an error when running any of the above commands, ignore it and proceed to run the remaining commands. This is normal and Voice Access will still work after running all of the commands.
Voice access will now work!! Enjoy."