Where can I buy S&P index funds?

Excuse me, I'm looking to invest in the S&P index funds but I'm not sure where I can buy them. Could you possibly provide me with some information on the best platforms or brokerages to purchase these funds? Are there any specific requirements or fees that I should be aware of before making my purchase? Additionally, is there a recommended minimum investment amount for getting started with S&P index funds? Thank you for your help.