You may want to include them in a sidebar of resources for the article. The editor may also require the names and numbers of your experts for fact-checking. Write the article. After you've completed your research, start writing the article while keeping the editor's specifications in mind. Don't send them an essay when they've asked for an article full of quotes from experts, for example.
Some people have difficulty starting an article.
Just start writing. Organize your thoughts and correct your spelling later. Begin an article with a line or paragraph from your query letter. Recycle your article. Once you've sold an article on a favorite topic, write another one or two or three.