Once the page is opened for R Markdown, there will be new radio buttons along the top side of the document. One of them will say 'MD'. Pressing this button will open a help page at the bottom right hand corner that lists all the necessary commands used in R Markdown, including those for formatting and styling.
As it can be seen from the image above, 'knit HTML' button will publish the contents of the rmd document into html version. The html file will be saved with the same name as the rmd file and will be saved at the same location. The preview page will also pop up at the same time. The below is an example of the preview pop-up page.