First of all you mast from this link http://www.adobe.com/cfusion/tdrc/index.cfm?product=after_effects , after download the software ,Open it ,Click TRY button like picture shown but if you have serial key click Install button
Then click ACCEPT button to continue
Now click SIGN IN button but if you don't have an account create on by clicking CREATE AN ACCOUNT ID , Us picture shown
Just wait for a few minutes to complete installing
