Multiplying the signal by a carrier frequency produces signals that are the sum and difference of the signal and local oscillator frequencies.

I have ben tasked to have a input complex signal at frequency of 250.01MHz. i have to mix this signal with a frequency at 250MHz. I understand that by mixing(multiplying) it will produce the sum and difference of the 2 frequencies. And i will use a low pass filter to filter out the sum frequencies. However, i cant seem to get how to multiply the signal with the frequency, Someone please help me. Below is my code:

close all;clear all;

    j=sqrt(-1);
    fsig = 250.01e6;
    fs = 1e6; %sampling frequency
    fc = 250e6; %frequency of USRP
    t= [0:1/fs:1];

    sig = exp(j*2*pi*fsig*t);