Upload a File (Video, Audio, PDF, etc.)

To upload files, you can use WordPress's online interface, the Dashboard.

To Upload a File in a Post

1. 1) On the Dashboard menu, click Posts, and then click Add New to display the "Add New Post" page.
2. 2) Click Add Media above the editor, either drop the file(s) or select from your computer.
3. 3) In the dialog box, select the file you want to upload.
   To select multiple files, hold down the SHIFT key (for PC users) or the COMMAND key (for Mac users).
4. 4) Click Open.
5. 5) When your file uploads, a field appears. At the bottom of the field, click the Insert into Post button.

To Upload a File in a Page

1. 1) On the Dashboard menu, click Pages, and then click Add New to display "Add New Page."
2. 2) Click Add Media above the editor, either drop the file(s) or select from your computer.
   
3. 3) In the dialog box, select the file you want to upload.
   To select multiple files, hold down the SHIFT key (for PC users) or the COMMAND key (for Mac users).
4. 4) Click the Open button.
5. 5) When the upload is complete, a field with your file appears. At the bottom of the field, click the Insert into Post button.

To Upload a File for Later Use (Using Media Library)

1. 1) On the Dashboard menu, click Media and then click Add New to display the "Upload New Media" page.
2. 2) Click the Select Files button to open a dialog box.
3. 3) In the dialog box, select the file you want to upload.
   To select multiple files, hold down the SHIFT key (for PC users) or the COMMAND key (for Mac users).
4. 4) Click the Open button.
5. 5) When the upload is complete, a field with your file details appears. Below the field, click Save all changes.

Original post: https://codex.wordpress.org/Uploading_Files