Adding actions to a custom GPT

Please forgive me if this is a stupid question but I’m an absolute beginner when it comes to this and learning as I go. I would like to create a GPT that can help me plan my Summer with my kids in the city where we live and I’m not sure where exactly to start. Of course I asked ChatGPT to help me with this and it recommended I integrate several API’s into it such as weather, events and activities, dining, etc. Where can I find these API’s? Is there a central location that lists API’s available for use within a ChatGPT model? Or do I just need to hunt for web apps that share their API’s and use those?