convolution mathematica
If it's a discrete serie of values, please take a look to the page 23 of "Discrete-Time Signal Processing" from Oppenheim, the second edition (the spanish edition, but i think it's the same in others editions).
The "method" in the book is:
1) Invert the time in the signal y[n], so you get: y[-k]=y[0-k]
2) Displace the signal by n, so you get: y[n-k]
3) Make the sum for every k, with a fixed n, for every n.
(It's a good idea to take a simple discrete signal as y[n], for example four values, and do the steps graphically)
result[n] = Σ (x[k]*y[n-k]), in the sum, k goes from -∞ to +∞.
It's hard to explain, so if you don't understand, (due my bad english), you better take a look to the book.
Or you can use the DFT to calculate each Fourier Transform, and multiply the results, but it depends on the type of series.
Regards, Diego