A desktop license is installed via the Workbench License Manager:
 

1) Copy the license order ID from your MyCLC account.
2) Start up your installed Workbench, by running it as an administrator (see related pages below).
3) If the License Manager window does not pop up while starting the Workbench, start it via the following menu option:
 

• Help | License Manager

Depending on your situation proceed as further described below: 
 

A: Upgrading from an earlier license for a given product

4) Click "Upgrade License".
5) Select "Download License" and click Next.
6) Click in the text field and paste in the Order ID.
7) Click Next, accept the license agreement and click Finish.
 

B: Running the Workbench for the first time, or where the license for your product is no longer valid

4) Select "Download License" and click Next.
5) Click in the text field and paste in the Order ID.
6) Click Next, accept the license agreement and click Finish.
 

C: Working on a machine that does not have access to the external network
How can I download a static license for a Workbench running on a non-networked machine?

Related pages:
Which tasks require me to run the Workbench as an administrative user and how?