Last month, the update was rolled out to Lenovo K3 Note, now the Lenovo A7000 has been receiving the Android 6.0 Marshmallow update. The over-the-air (OTA)update also includes Android security patch for the month of March as well.
The update weighs tipping the scale at 1.3GB, so we recommend you to turn in your Wi-Fi before heading to download the update. The update is staged, so it will take some time to hit your device. However, if you are feeling impatient, you can manually check for it by heading to the Settings menu on your device.