As Hood says, it is as simple as that.
Are you asking how to wire up the relay as well ?
I wired up four relays on my machine to turn on the motor and coolant (still to do the coolant, but the relays are there)
The easiest way is to drive the relays via a Darlington array, direct from your LPT1 port (or from your breakout board). A Darlington array is a power amplifier, and all the circuitry is contained in a 16 or 18 pin chip, which contains 7 or 8 seperate circuits. The cost less that £1 in UK from Maplin.
The circuits can each sink 1/2 amp and can be wired in parrallel to increase that. They take in a GND wire from your computer and a positive supply to drive your relays (whatever voltage you need). They are simple and easy to use, and do not need any additional diodes, etc.