You just need to click here.
this page will direct you to the download page of your antivirus.
Download 32 or 64 bit whatever you want.
Install it on your computer and enter your key on cd
This was a common or normal man's approach.
There is also an advanced approach to this problem bit tricky for layman's in this field.
there are various image mounting tools such as Daemon Tools Lite or Daemon Tools Pro.Choice for the product depends whether you go for pro or not.These create a virtual drive in your pc which is a dvd drive(note this is virtual)
Now comes the very important and interesting part.
also install daemon tools on your friends pc and make an image of your cd from friends pc.
Carry this image in a flash drive and paste in your pc.
now open daemon tools and mount this image.
Mounting image means your compurer will assume that now have another dvd drive and this has your av cd inserted into it.
believe can't get better than this
this approach is better because this overrides any sort of problem reguarding key if it happens.
moreover it's excellent for playing games as cd is always unscratched.
That ends all.
Enjoy your antivirus guy......