How do I put balance on my STC?

Hello there, I'm curious about how to add funds or balance to my STC account. Could you please guide me through the process step-by-step? I'm new to this and want to make sure I do it correctly. Is there a specific platform or method I should use? Also, are there any fees associated with adding balance to my STC account? I'd appreciate any insights you can provide. Thank you in advance!