Did you try going into "Settings" and then "Language & input"? It should be in there to turn the option off or on.
It may also be in "Settings" then "Additional Settings", then "Language & input". From here you go into "TouchPal for OPPO" and change it in there.
Personally I find TouchPal and its options annoying. I have the whole thing turned off on my device.
Done via "Settings", "Apps" then "All" and then I disable the app. However not all devices allow you to disable it, should you choose to.