Sales tax is not on your W2. You mean your tax return? That is an Itemized Deduction so you need to use the Deluxe version to enter Sales Tax.
You can type sales taxes paid in the search box at the top of your return and click Find and it will give you a link to Jump To it.
OR
Enter Sales Tax under
Federal
Deductions and Credits
Then scroll down to Estimates and Other Taxes Paid
Sales Tax- click the Start or Update button