To change the ringtone on the TCL Onetouch 4043, follow these steps:

1. access the settings:
- From the home screen, press the OK button and select the "Settings" icon.

2. select profiles or sound mode:
- Navigate to the "Settings" and select "Profiles" or "Sound mode". Here you can select different profiles such as "Normal", "Silent", "Meeting", "Indoor" or "Outdoor", which often contain predefined ringtones.

3. change ringtone:
- If you want to change specific ringtones, navigate to "Sound Mode" or "Profiles" within the settings and select the desired ringtone. Some models allow you to choose between different pre-installed ringtones or even add customised tones if this option is available.

4. customised ringtone (if available):
- Some models allow you to add custom ringtones. To do this, you would need to search for an option such as "Custom ringtone" or "Change ringtone" in the settings and select or upload the desired tone.

Follow these steps to change the ringtone of your TCL Onetouch 4043.