Amplify 0 to 3.3V input to +/-3.3V
It's easier if you think of the circuit as an inverting configuration







simulate this circuit &ndash; Schematic created using CircuitLab

The voltage across R1 is 3.3 - V2, so the output is $$ V_O = 3.3 - 2(3.3-V2) = -3.3 + 2V2$$ Keep in mind that for this to be accurate, the 3.3 has to be very accurately matched to the 3.3 reference of the DAC. Any mismatch will result in a zero shift.