The expression "as I see fit" means "as I consider something desirable and/or necessary." The best and closest French expression is comme bon me semble, or, according to the pronoun or noun used, comme bon te chante, and so on.
Consider the following examples:
- "Modify it as you see fit. But act quickly because the customer is getting impatient."
- "She can work as many hours as she sees fit, as long as the project is done and her boss is happy."
- "Why didn't you see fit to inform us of your future plans?"