ESP8266

Hello Guyz, I am working on ESP01 wifi project with Arduino IDE 1.8.2. but whenever i tried to work on ESP8266.h it gives me error like

warning: espcomm_sync failed
error: espcomm_open failed
error: espcomm_upload_mem failed
error: espcomm_upload_mem failed

Ive already install ESP8266 Generic Board.

Please give me advice. Thank you.