The steps to set ringtones on Ringtone Duoduo are as follows:

1. Open the desktop of your mobile phone and click on the icon of Ringtone Duoduo.

2. After entering the page, you will see 5 options below, find the category and click on it.

3. After clicking, you can search for the song you want in the search box.

4. Search for the ringtone you need, and the desired ringtone will appear.

5. Then find this ringtone and click it, come out to settings, and click it again.

6. Then it will come up to set this ringtone as the phone's ringtone. You can select the ringtone for incoming calls, and then click OK.