How to activate GTC?

Excuse me, could you kindly explain the process for activating GTC in a step-by-step manner? I'm a bit confused about the procedure and would appreciate your guidance. Is there a specific platform or application where I need to go to initiate the activation? Are there any prerequisites or conditions that I need to fulfill before I can proceed with the activation? Your detailed explanation would be extremely helpful in clarifying this matter for me. Thank you in advance for your assistance.