Q: windows 8.1 installer is not starting after bootcamp partition in Mac air 2015

Hello,

My PC: mac air 13 inch (OS X Yosemite 10.10.4) early 2015 version

This is new Mac air note book

1) I bought windows 8.1 64 bit pro for students from Microsoft

2) Downloaded windows software by online and got ISO file and saved in USB drive using windows Notebook

2A) copied that win ISO file from USB to Apple Mac air desktop

3) Using Boot camp assistant , created partition in hard disk and installed windows ISO file in USB (Lexar brand 2.0 | 16GB)

4) after that I could see Boot Camp (FAT 32) partition

5) I could not get windows installer screen to install windows..I assume that it should come up automatically

I tried many times...Please help me or any idea

Thanks