How do I buy a Stake in the us?

How do I acquire a stake in the US cryptocurrency market? I'm new to this and want to understand the process of purchasing tokens or coins that are traded in the US. Are there any specific platforms or exchanges that I should use? Are there any regulations or legal considerations that I need to be aware of before making any investments? Can you provide a step-by-step guide on how to buy a stake in the US cryptocurrency market?