Here’s my Remote Spark example web app with functions and variables:
It uses the simple jQuery POST and GET requests that Dave mentioned above.
If I were you I would just run the example locally in your browser and play around with the code first. Then when you get to the point you have something you like, find a place to host the files. For many years I’ve hosted websites for myself and family, so I have FTP access to put files up there whenever I want. I haven’t really looked around for free sites lately, but I’m sure some people will have suggestions. I should have a couple myself so I’ll probably go look and see what’s out there today in the way of simple web hosts.
I didn’t see a question about the access_token, but if you are wondering where you can find it…
And the core ID:
It may seem overwhelming at first, but just experiment with one thing at a time and slowly start stacking all of your knowledge together until you have created a masterpiece! We are here to help 
and with patience we’ll get through it together!