A simple task like change a ringtone on a phone can be hard to find on P168's menu.
Here are the steps to change them with some other bundled or with the ones you download or even with a full MP3 song.

Go to Home menu
* System
* User Profile
Here select the one you use and then choose Customize
* Tone Setup
* Incoming call
Here you can pick one (from 1 to 25 are predefined on the phone) or add one in the 26 to 30 slots.
If you choose to add one click the slot desired (26 to 30) and then click OK.
* Replace
Here it shows the memory card
Go to 'My music' folder or wherever you have the sounds you like
Choose the ringtone or MP3 you like and then click OK

Now you have the sound you want for the ringtone.

Many people asked and as far as i know there is no way to add more than five custom songs or ringtones because the only slots left are the 26 to 30 and the 1 to 25 doesn't permit to change them.
We'll have to wait for a way to update the firmware for that to happen.

Worked for you ? please vote for me.