The Log in button is a planned feature which, among other benefits to be announced, will allow the installer of the software to “pull” the serial numbers associated with their SOLIDWORKS ID to populate the serial numbers for their products.

This will be beneficial in environments where an administrator wants to manage the products assigned to their SOLIDWORKS users.  An admin can add products to the user, avoiding the need to send him serial numbers.  The user will not need to maintain his own list of serial numbers and match them to the correct products. They'd just log in.  However, this will require tools for the administrator to see their users, assets, and assignments.  Those tools are not available in Beta1, so the Log in button is disabled.  We are targeting Beta2 for releasing the tools and the login feature.