When editing a page or post, you can add media by clicking the “Add Media” button .
You can then drop an image, word doc, or pdf from your computer into the upload dropzone, or select the files you want. If an image has already been uploaded into WordPress, you can select it from the Media Library, which stores all the media you may have uploaded into your blog. You will then have a variety of layout options to place the media into the page.
If you just want to upload media and add it to a post or page later, you can either select the “+New” menu item from the top navigation. Or, you can select the Media menu item on the left menu bar.
All uploaded files are stored in your site’s “Media Library,” which allows you to store images, and a number of common document types (PDFs, Excel, Word documents, etc.). Try not to upload video files, however, as these can be large files.