Follow the following steps:

1. First, open Netease Cloud

2. Click the search symbol in the upper right corner

3. Search for the song you want to use as a ringtone. When you find it, click "Download" and wait for the download to be completed.

4. After downloading, click the three points on the right of the song again. At this time, "Set as ringtone" will appear below. Just click it.

Reference link: Baidu Encyclopedia-ringtone