Welcome to Apollo's Little Guide on how to start modding! And no I don't plan to make a video on this.
This is a tutorial after 5 days of modding, I may get some terms wrong
Yes, if you are determined you can understand a lot instead of asking for a spoonfeed
Let's get started! Head on to https://docs.reactor.gg and follow the documentation, come back here after you've got your first mod created!