Where do I enter in my cash tips?

To enter your tips: Open or continue your return in TurboTax, if you aren't already in it. Search for 'W-2' and select the Jump to link in the search results. 

If that employer's W-2 was already entered on the Your W-2 info so far screen, select Edit next to that employer.

1. Select the box for Unreported tips and select Continue.
2. On the Now let's enter your unreported tips screen, enter the amount of your tips.

Here's more info on How to Enter Unreported Tips. 

If your tips were reported to your employer they should be on included in your gross income on your W-2 in box 1.  The tips reported by you to the employer will be entered in box 7.