We converted my basement to a hair salon. Where would I enter those expenses (construction, tile, A/C, etc.)?

The costs of converting part of your home to a business use are not considered business 'expenses' - they are treated as either business assets or improvements to your home.

If you treat them as business assets, you can claim a depreciation expense -   enter them in the Business Asset interview of TurboTax Self-Employed (or Home and Business and depreciate (expense) them over 27.5 years. 

If you choose to treat them as improvements to your home, they get added to the cost basis of your home and will get taken into account when calculating any gain(loss) when you sell.