Using a root explorer got to /System/ and open the txt file calles build.prop and add this line to the end of the build prop ( a new line at the end )
qemu.hw.mainkeys=0
save and reboot
Using a root explorer got to /System/ and open the txt file calles build.prop and add this line to the end of the build prop ( a new line at the end )
qemu.hw.mainkeys=0
save and reboot