Xiaomi has started the rollout for the MIUI 8 global beta ROM. Select devices from the company will be getting the update today, and the rest of the supported devices will follow. The list of devices getting the update today includes the Redmi Note, Redmi Note 4G, Redmi Note Prime, and Mi Max 32GB. Those on the MIUI Global Developer ROM have it the easiest, as they can just download the OTA update. Those on the Alpha ROM will have to first flash the Developer ROM and then install the OTA update. Those on stable ROMs will have to first unlock the bootloader and then manually...
Source: http://www.gsmarena.com/miui_8_global_beta_rom_now_available_for_select_devices-news-19322.php