The easiest way to get there is to type the words union dues in the Find window on the upper right, hit enter, and then click the Jump To below. Just keep going in that interview until you see the screen that allows you to enter the amount of union dues. There will be one or two screens after you enter union dues, then you'll return to a little summary showing you all your job-related expenses.
You will also see the other job-related expenses you can deduct so maybe you'll find something else that you didn't realize could be deducted. If you have any questions about those other expenses, please post back here.
You should be aware that union dues fall into the miscellaneous category, where 2% of your Adjusted Gross Income is subtracted from the amounts you enter. You then receive a deduction only for the amount OVER 2% of your AGI.
You won't see any change in your refund or tax due until the total of ALL your itemized deductions exceeds your standard deduction. That's because the program starts out with giving everyone their standard deduction. When and if you have enough itemized deductions to exceed the standard, the program switches you over to standard. You don't get to take the standard deduction plus a few itemized deductions. It's always one or the other.
You should also be aware that you don't always get a deduction for the amount you enter. Just as your union dues are limited to the amount over 2% of your AGI, other deductions can also be limited. For example, medical expenses are limited to the amount OVER 10% of your Adjusted Gross Income (7.5% if 65 or over).
Lastly, your deductions don't increase your refund by the amount of the deduction. Rather, they increase your refund by the amount of tax you would have paid on the amount of the deduction. Deductions can only get you back tax you've had withheld. If you are already getting back all that you had withheld, you won't see any increase in your refund.
