Yes, you can deduct legal fees for your BP settlement.
To deduct legal fees, you must itemize deductions on Schedule A, and the sum total of your miscellaneous deductions including your legal fees must exceed 2% of your Adjusted Gross Income.
Given the above limitations you may not be able to benefit from your legal expenses.
To enter your legal expenses:
Type in legal expenses, deduction the search box, top right of your screen, then click the magnifying glass
Click the jump to legal expenses, deduction link in the search results
Follow to prompts and online instructions