You should use "prefer for" when you are talking about a specific thing or object.
Here are some examples:
Prefer to:
* I prefer to eat breakfast at home.
* She prefers to work on her laptop.
* They prefer to travel by train.
Prefer for:
* I prefer for my coffee to be strong.
* She prefers for her phone to have a good camera.
* They prefer for their vacation to be relaxing.
In essence:
* "Prefer to" is followed by a verb (action).
* "Prefer for" is followed by a noun (object).
Let me know if you have any other questions!