How to buy a RRIF?

Could you please elaborate on the steps involved in purchasing a Registered Retirement Income Fund (RRIF)? As someone who is interested in planning for my retirement, I'm curious about the process and what factors I should consider before making such an investment. Are there any specific requirements or documentation I need to prepare? Additionally, are there any tax implications associated with buying an RRIF that I should be aware of? I would appreciate a clear and concise guide to help me navigate this process.