You can upload and insert media (images, documents, etc.) by clicking the Add Media button.
Selecting Images or Files
You can select from the images and files already uploaded to the Media Library, or upload new media to add to your page or post.
Click to select the image or file that you would like to add to the page.
Optionally, change the Attachment details on the right-hand side of the Insert Media window.
When you are finished, click Insert into post.
To create an image gallery, select the images to add and click the “Create gallery” button.
Click each of the images you would like to include in the gallery, then click Create a new gallery.