Writing custom content creation tutorials is a very time consuming business. It is not the purpose of this website to provide teaching AND more importantly, there are plenty of other sites that do have extensive help available for new creators.
Thousands of people have asked me to teach them how to make Sims content over the years, and sometimes I do wonder what they are actually expecting me to say in reply. It is an absolutely vast subject area, anything technical is enormously complicated and takes years to understand so obviously there's nothing particularly useful that I could say to them in a quick email...
... other than of course this - the single most useful thing you need to know if you are interested in making your own custom content is...
Learn to use the internet
Learning how to search online for tutorials and answers to specific creation related questions WILL be quicker and more productive than asking some creator to give you personal tuition. Whilst there are plenty of community forums where you can go and ask questions and get help with creating problems, there are none (that I know of) who will cheerfully help new members who ask extremely general questions like 'how do I make my own custom content' without having done at least a bit of research first.
If you don't know what a search engine is and how to use one then I recommend this topic provided by the BBC:
The big problem with asking a creator to give you a tutorial to study is that it doesn't give you many options if you don't understand the tutorial, if it was out of date or just badly written. You then have to go back to the creator you pestered for help and demand more help, or of course give up on the whole idea.
In the immortal words of Terry Pratchett "Give a man a fire and he's warm for a day, set a man on fire and he'll be warm for the rest of his life". If you've no idea where to get help, where to go next or how to find answers to your questions, then you'll be forever stuck waiting for someone to help you. Learning to find resources yourself means you'll also learn much faster as well as finding out good places to go where you can ask specific questions from qualified volunteers (rather than asking some random creator for help via their website).