I don't understand how to work with an API from a website with C++. Something about sending a packet? I can only find online tutorials for the Windows API. So how do you do it?
I don't really follow? If you mean what I think you mean then Google "sockets in C++" or similar. C++ doesn't even know what a packet is let alone how to send one. You'd need an API. The Berkeley Sockets API is probably the most generic, or WinSock. Beej's guide was the de-facto learning resource for sockets when I was learning C++ some 15 years ago. No idea if it still is but website is still there tho: http://beej.us/guide/bgnet/
API stands for Application Programming Interface and consist by a set of functions exposed by an object [DLL, EXE]. I can't see how a website can expose an API... maybe their can for their backend because that is the place where objects reside for a website, the backend. You as an user are the front end, and I can't see how you can call an API in this case.