How do I buy an S&P index fund?

Excuse me, could you please explain the process of purchasing an S&P index fund in a simple manner? I'm a bit new to the world of investing and would like to know the steps I need to take to invest in this type of fund. Specifically, I'm wondering about the different options available for buying into an S&P index fund, whether it's through a brokerage account, an exchange-traded fund (ETF), or some other method. Additionally, I'd like to know if there are any specific considerations I should keep in mind when making this investment, such as fees, taxes, or the potential risks involved. Thank you for your help.