Noob ISR C Code Question

Depends on which toolchain you use. The IAR documentation explains how to do this for that tool.

Here's an example from MSP430Ware (examples/driverlib/MSP430F5xx_6xx/usci_a_uart/usci_a_uart_ex1_rx.c)

#pragma vector=USCI_A0_VECTOR
__interrupt void USCI_A0_ISR (void)
{
    switch (__even_in_range(UCA0IV,4)){
        //Vector 2 - RXIFG
        case 2:

            //USCI_A0 TX buffer ready?
            while (!USCI_A_UART_getInterruptStatus(USCI_A0_BASE,
                       USCI_A_UART_TRANSMIT_INTERRUPT_FLAG)) ;

            //Receive the data
            receivedData = USCI_A_UART_receiveData(USCI_A0_BASE);

            //Echo received data
            USCI_A_UART_transmitData(USCI_A0_BASE,
            receivedData);

            break;
        default: break;
    }
}

There's a better example for you in the MSP430Ware library:

examples/driverlib/MPS430F5xx_6xx/timer_b/timer_b_ex1_continuousModeCCR0.c

Also, reference this post on how the peripherals and corresponding vectors are named.