Now i have a hex file ,but i don't know how to download.
Here is a discussion of one way:
Avrdude tool is a way also. IDE has not an option to upload HEX directly. You can set on logging during the upload in IDE preferences, upload something, look at the commands used and use them by analogy.
Download the software. You know where hex file being saved. if not check preference section. Once you get hex file choose hex file , choose the board, baudrate & upload.