Hi,
Welcome to blogger Forum,
Add image or video
1. On your post > Select image/video icon in compose mode.
2. Now here you have some options to upload your image or video:
3. Finally you can see your image with the post:
Upload music
Blogger
does not have native tool to upload music like image or video, but you
can use your channel of youtube to share your audios, also you can check
"Soundcloud" then insert the player's HTML code into your blog.
Best regards,