Please follow these steps:

1- Please go to Albums.

2- Create new Album.

3- Click on "add media" button

4- Upload your audio and video

5- If you want your audio/video will display on your post then click on "Insert into post" otherwise ignore this step.

6- After completion close it

7- Update / Save it

If you want to remove your audio and video than please go to Media and remove it using delete option.