Policy is applied when the computer starts and when the user logs on. When a user turns on the computer, the system applies computer policy. When a user logs on interactively, the system loads the user profile, then applies user policy.

When you apply GPO computer settings are applied at?

The Computer section of a GPO is applied during boot. The User section of a GPO is applied at user login. User GPO processing can be configured three different ways, as documented below.

How do I know if my GPO is applied?

Press the Windows key + R to open the Run box. Type rsop. msc and press Enter. The Resultant Set of Policy tool will start scanning your system for applied group policies.