I purchased tubotax 2021 CD version. I already download Mac version using license number. I need to download Mac version for another filing. Where I can download it?

For another computer?   Or for the same computer?   One install can do unlimited returns.

You can download it again the same way.   Log into your account.  

Access your downloads here

https://shop.turbotax.intuit.com/commerce/account/secure/login.jsp?pagecontext=download

How to download your software purchase

https://ttlc.intuit.com/community/installing/help/how-do-i-download-the-software-i-purchased-at-turbotax-com/00/26075

I already download Mac version using license number. I need to download Mac version...

Do you mean you now need the Windows version?

you r right.  There was typo in my original post.

My question is how to download Windows version after downloading Mac version? 

You need to call in to get the other download.

Contact Customer Service
5am-5pm Pacific Time
Monday-Friday
https://support.turbotax.intuit.com/contact/

What is the Turbo Tax phone number
https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632