Nowhere. The standard deduction is automatic based on your filing status.
Check your 1040 line 9 to see if you got the right Standard Deduction.
For 2019 the standard deduction amounts are:
Single 12,200 + 1,650 for 65 and over or blind
HOH 18,350 + 1,650for 65 and over or blind
Joint 24,400+ 1,300 for each 65 and over or blind
Married filing Separate 12,200 + 1,300 for 65 and over or blind
Before filing, you can preview the 1040 or print the whole return