Use Basic English vocabulary and shorter sentences. This allows people to understand normally complex terms or phrases.
Write good pages. The best encyclopedia pages have useful, well-written information.
Use the pages to learn and teach. These pages can help people learn English. You can also use them to make a new Wikipedia to help other people.
Simple does not mean short. Writing in Simple English means that simple words are used. It does not mean readers want basic information. Articles do not have to be short to be simple; expand articles, add details, but use basic vocabulary.
Be bold! Your article does not have to be perfect, because other editors will fix it and make it better. And most importantly, do not be afraid to start and make articles better yourself.