Why is my coils in the attic freezing up ithought it only freeze up outside.what can I do to fix it

The evaporator coil will freeze up do to lack of air flow (dirty coils, dirty filter) or low on refrigerant do to a leak

esquire1 is exactly right. Check filter, make sure all supply registers are open, also make sure your return grills are not covered. If all of these things check out OK, you should call a pro. Checking system charge, and or cleaning coils may be necessary.