Mario,
While the license is legally needed, there is no way to apply the license inside of SnapCenter 2.0.
The license is required, but it is not enforced or applied in any way.
Since there is no enforcement the message that appears was required to inform users that they need to acquire the license if they have not already done so.
The message can be closed by clicking the "X" in the upper right corner of the message (it is a bit hard to see).
Licenses will be enforced in the next release of SnapCenter.
Hope this helps,
John