After installing, you will automatically be prompted to enter your License Key to activate your product. If you skipped this step, or your product is still not activated, follow the steps below:

1. Open your Windows ESET product. If your product is not activated, your main window will be red:
   
   

2. Click Help and support → Change License.
   
   

3. Click Use a purchased License Key. 
   
   

4. Type or copy/paste your ESET-issued License Key into the License Key field and then click Continue. Make sure you enter the License Key exactly as it appears and include the hyphens. If you copy/paste be sure you don't accidentally select additional space around the text. Click here if you lost your License Key.
   
   

5. Click Activate.
   
   

6. Click Done. You have successfully activated your product.
   
   

If activation fails with an error, see I received an activation error while installing my ESET product—what does it mean?