Just Finished My First Build Ned Help Installing Windows!

I just finished my first ever build and everything seems to be working fine. Cpu and mobo temps are 35 C pu is being detected. The ony issue i had was with my HDD. It was a spare from a previous PC but i found another one which is working fine. It has windows on it but it wont boot up i guess because different hardware and drivers which is fine because im doing a clean install. So i accidentally formatted my usb with my Windwos 7 64bit iso which i made using a friends pc. I have a macbook and i dont know how to make a bootable windwos 7 usb. I have a couple windows cds but i didnt buy and optical drive for it. So I'm wondering if anyone can  help me recreate the bootable usb using my macbook pro, Thank you. Sorry if there is any confusion.

Although I have no experience with Apple computers a quick search in Google provided me with the following video on youtube called "How to Create a Bootable Windows 7 USB on a Mac": link

Hope it helps!

Doing it right now hope it works. Thanks for the feedback