How do I buy arbitrum on Coinbase?

I'm quite interested in investing in cryptocurrencies, and Arbitrum seems to be a promising option. Could you please explain to me the process of buying Arbitrum on Coinbase? Is there a specific way I need to set up my account first? Also, are there any fees or limits I should be aware of? I'd appreciate it if you could provide a step-by-step guide, as I'm still relatively new to this field. Thank you for your help!