If the fee is applied as part of a purchase, it can be added to your basis in the asset. If it is applied to the sale, it can be subtracted from the sales price. Include the cost when you enter a purchase or a sale as applicable.
Otherwise, broker fees for managing investments aren't deductible under current Federal law as miscellaneous itemized deductions. If you live in a state that still allows miscellaneous itemized deductions, you can enter then in the Federal section and the information will flow through to your state return.