Enter these commands in Android device Terminal
su
setprop service.adb.tcp.port 5555
stop adbd
start adbd
After this, you can use CMD and ADB to connect using the following command
adb connect 192.168.0.101.5555
And you can disable it and return ADB to listening on USB with
setprop service.adb.tcp.port -1
stop adbd
start adbd
From a computer, if you have USB access already (no root required)
It is even easier to switch to using Wi-Fi, if you already have USB. From a command line on the computer that has the device connected via USB, issue the commands
adb tcpip 5555
adb connect 192.168.0.101:5555
Replace 192.168.0.101 with device IP