Start by finding new sources and adding & citing new information to these "stubs." You can add the word "stubs" to a search to find short articles that have been labeled for improvement. To see an example, Google "Wikipedia actor stubs."
Women in Red refers to a project to make lists of women in all subject areas who are notable and should be included on Wikipedia. Working on a Woman in Red means creating a new article from scratch. Don't let this stop you: you can always start with a stub, and work to expand it later!
To get full permissions to be an editor, you need to make at least 10 edits. If you make a major edit before you have full permissions (like removing a paragraph from an established page), it will be flagged almost immediately.
A good way to practice editing is to make smaller edits, like grammatical edits or citation edits. Unsure where to add citations? Try Wikipedia's Citation Hunt.