How do I get MATIC on Polygon mainnet?

Excuse me, could you please elaborate on the process of acquiring MATIC tokens on the Polygon mainnet? I'm relatively new to this and would appreciate a step-by-step guide. What are the prerequisites I need to fulfill? Are there any specific platforms or exchanges that I should use? Also, what are the fees associated with the transaction, and how can I ensure the security of my tokens once they're on the Polygon mainnet? Thank you in advance for your assistance.