The steps to add music to a video and share it on Moments are as follows:

1. Open Douyin, select the video to be uploaded to Moments, and click the share icon on the right side of the video .

2. Click "Save to Album" under the sharing page to save the video to the mobile phone album.

3. Open WeChat, click the "Discover" option, and then click the "Moments" option.

4. In the Moments page, long press the camera icon in the upper right corner to enter the Moments editing page.

5. In the editing page, click the "Album" icon in the lower left corner and select "Select from Mobile Album".

6. Select the saved video in the album and click the "Done" button in the upper right corner.

7. In the Moments editing page, enter the text content you want to express and click the "Who can see" option.

8. In the "Partially Visible" option, click the "Select from Address Book" option and select the friends who need to be visible.

9. Click the "Finish" button to publish the video and music to your circle of friends.

Through the above steps, you can add music to the video and share it with your friends.