If you also want to do an offline activation then these are the instructions found in the FAQs
SONAR Platinum/Professional/Artist Offline Activation
Access to the Internet from another computer is necessary in order to download the SONAR installers and to transfer the activation files. SONAR Platinum and SONAR Professional users should note that Addictive Drums 2 can only be installed on a computer with an Internet connection.
Visit your Cakewalk account to download the SONAR installers and transfer them to your offline computer.
After installing SONAR, open the Help menu > Offline Activation > Export Activation Request to open the Save activation request dialog box.
Note that this menu option will not be available after SONAR has been activated.
Select the folder to which you want to save the activation request, then click Save. This generates an activation request file with a .crq extension.
Tip: save this file to a convenient location, like your Desktop or Documents folder, so it will be easy to find in the upcoming steps.
Copy the .crq file to an online computer (using a USB drive, for example).
Using an online computer, open the Activate section of your Cakewalk account. Sign in with your Cakewalk username and password if necessary.
Click the Select a File button to upload the .crq file.
Click the Submit button. Your browser will begin downloading the activation response file, which has a .dat extension.
Internet Explorer users must also click Save for the file to download.
Transfer the .dat file to the offline computer. It will most likely be available in the online computer's Downloads folder.
Open SONAR's Help menu > Offline Activation > Import Activation Response to open the Import activation response dialog box.
Select the .dat file that you downloaded and click Open. A toast notification will let you know that SONAR is activated and ready to use.
If activation fails, contact Cakewalk support.