There are 2 ways to do this:
From My library
If you’d like guidance, read: How do I activate the code for my teaching materials on Cambridge One?
From your class page:
1. Go to the Materials tab, then choose Tests
2. Select Activate course material
3. Then enter your activation code and select Activate
You'll see confirmation of:
Duration of your access
Title you have activated
The last day of your access.
Now you will have access to the Tests.
Please note that activation codes can be found printed in the Teacher's book.
Tip: If your Teacher’s book does not include a code, please contact your English Sales Representative by selecting your location.