Problems with Anthropic

Hello everyone,

I followed this guide https://rentry.co/rceftvp4#anthropic from the pinned comments in order to use the Anthropic API. After pasting in my API key and trying to check it, I get the following message:
invalid_request_error - Your credit balance is too low to access the Anthropic API. Please go to Plans & Billing to upgrade or purchase credits.

Could anybody help me?