I am a full time student and my parents can claim me. There is no where to decline the standard deduction.

You do not decline the standard deduction.  What you have to do that is very important is to say in MY INFO that you can be claimed as someone else's dependent.   When it asks you if you can be claimed make sure you say YES.   

You may want to itemize deductions if your standard deduction is limited because another taxpayer claims you as a dependent.

To switch from itemized to standard deduction (or vice versa):

1. Open your tax return and select Federal, then Deductions & Credits.
2. Scroll to the bottom and select Continue.
3. Answer all the questions, until you get to the screen Based on what you just told us, the Standard Deduction is best for you or Based on what you just told us, itemizing deductions is best for you.
4. On that screen, select Change my deduction.
   • You'll see a pop-up showing how much each deduction is worth.
5. If you want to change your deduction, select it and Continue.
6. If you don't want to change your deduction, select Cancel.

TurboTax FAQ: How do I change from the standard deduction to itemized (or vice-versa)?