As a new editor, you may feel a little overwhelmed by the sheer size and scope of Wikipedia. Don't fret! Here are some resources that you can look into:
The contributing to Wikipedia page provides information, links, videos and other resources on the basics needed to edit Wikipedia.
Your first article: an article that discusses some of the dos and don'ts, then shows you how to create an article. Note: The ability to create articles directly in mainspace is restricted to autoconfirmed users, though non-confirmed users and non-registered users can submit a proposed article through the Articles for Creation process, where it will be reviewed and considered for publication.
Introduction to navigating Wikipedia: a seven-part guide to navigating Wikipedia: Introduction; Namespaces; Searching pages; Page histories; Redirects and shortcuts; Useful links; and Summary.
Introduction to editing: a six-part guide to editing: Editing pages; Formatting; Links and wikilinks; Saving your changes; Creating new articles; and Summary.
Introduction to referencing: a five-part introduction to referencing: Verifiability; Inline citations; RefToolbar; Reliable sources; and Summary.
Introduction to uploading images: a four-part guide on uploading images: Introduction; Uploading images; Using an image; and Summary.
Introduction to tables: a four-part guide to putting tables in pages: Introduction to tables; Editing tables; Expanding tables; and Summary.
Introduction to talk pages: a six-part guide to using talk pages: Talk pages; User talk pages; Layout; Examples; Drawing attention; and Summary.
Editing with VisualEditor
Introduction to editing with VisualEditor: a six-part introduction to editing with VisualEditor: Opening the editor; Toolbar basics; Links and wikilinks; Publishing changes; Creating new articles; and Summary.
Introduction to referencing with VisualEditor: a six-part introduction to referencing: Verifiability; Adding references; Editing existing ones; Reusing references; Reliable sources; and Summary.
Introduction to tables with VisualEditor: a five-part guide to putting tables in pages: Introduction to tables; Editing tables; Adding new tables; Expanding tables; and Summary.
Training for students: students start here! A four-part, 57-page training intended for students doing assignments on Wikipedia, with more detailed introductions to core Wikipedia policies, editing basics, and more specific editing advice for students. Chapters: Welcome (4 pages); The Core (14 pages); Editing (24 pages); and Advanced and background (15 pages).
Training for educators: educators start here! A five-part, 97-page training for professors and other educators who want to run Wikipedia assignments for class, with introductions to core Wikipedia policies, editing basics, and an overview of best practices for designing and implementing Wikipedia assignments.
Plain and simple non-free content guide: discusses how Wikipedia's copyright guidelines are probably the most complicated part of the whole site, and breaks down what the rules are and what they mean.