How do I buy a SPX index fund?

Excuse me, could you please elaborate on the process of purchasing a SPX index fund? I'm interested in diversifying my portfolio and investing in the S&P 500, but I'm not entirely sure where to start. What platforms or brokers offer access to these funds? Do I need to meet any specific criteria or have a certain amount of capital to invest? Also, how do I determine which SPX index fund is the best fit for my investment goals and risk tolerance? Thank you for your time and assistance.