I purchased turbotax premier mac version 5 user product. I need to download windows version of it as well. Can you please help me?

If you subscribe to the Turbotax Advantage program, you automatically get both versions.  (Think about it for next year.)

For this year, I don't know if you can get the freebie, you will have to ask customer support by phone. 

https://support.turbotax.intuit.com/contact/

Also, it's not a "5 user" product.  The license allows only you to use the program, although you can install it on more than one computer that you own and prepare more than one tax return (for family and friends, no commercial use allowed).  You can e-file up to 5, that is an IRS rule not a Turbotax rule.  And if you have already filed 5, you can't get 5 more by buying a new copy because the limit is per taxpayer by the IRS.

So one user, more than one computer that you own, up to 5 e-filed returns.  Call support if you need to install on a different OS.