Ask "for" is to ask someone to do get something for you.
Ask "to" is to ask someone to do something for you. 
If you ask for something, it means that you want someone to give you something:
I always ask for extra tomato sauce on my pizza.
They asked their boss for more money, but he refused.

Ask to is to talk about requesting something:
She asked to see Professor Fenton. (ask + to-infinitive)
We asked the City Council to help us organise a sports day