The last post in this thread is over 60 days old. Posting in this thread will be considered a bump, so please make an attempt to be courteous if you go ahead with it.
If the last post is over 6 months old, it may instead be a better idea to start a new topic. If you aren't sure about what to do, feel free to ask a staff member for help, or try to locate a 'general questions'-type thread if it exists in this (sub-)forum.
You start with an idea, and a willingness to be independent. Asking for help if you've run into a problem is one thing, but asking others to do things like actually doing the coding and assets for you is certainly frowned upon.
You then hop over to the CSTSF Modding Discord and look in their #modding-tutorials channel. As far as I know, those resources are the most up to date and focus more on Booster's Lab rather than Cave Editor, which is what the basic editor's guide on the Tribute Site focuses on. That also seems to be the place where Cave Story modders are most active, but...I could be wrong.