Note: To install MIUI 9 on your Xiaomi device using XiaoMiFlash tool, you need to have a bootloader unlocked device. 1. First, download the latest version of the XiaoMiFlash tool for your PC, available for free, from here and install it. 2. Once you've installed the flash tool, turn off your Xiaomi device.
Go to Settings -> About Phone -> Check for Software Update. The update will be available across the globe but as it is being rolled out in a phased manner, it may take some time to be available in every region, but if you want you can manually Download and Install Redmi 4A MIUI 9.5.5.0 Global Stable ROM.qdFIxvn.