I had to travel in my nursing job to do assessments on potential patients for assisted living. How do I claim these miles, or gas used,

It depends.  If you are a W-2 employee, the mileage is not deductible, because unreimbursed employee expenses are not allowed, through 2025 (see: Are Unreimbursed Employee Expenses Deductible?).  

If you are self-employed, vehicle expenses are deductible.  You can choose mileage or actual expenses. In order to claim vehicle expenses and mileage, you need to add a vehicle to your business; here are the steps in TurboTax Online:

1. Navigate to Federal > Wages & Income > Self-employment income and expenses
2. Edit your business 
3. Choose add expenses for this work
4. Choose Vehicle and Continue
5. Vehicle now appears in the list of expenses, choose the pencil icon to the right of vehicle expenses
6. Answer the interview questions about the vehicle, and enter the related expenses