It's not too complicated
Just get your group certificate (I'm assuming this is the piece of paper you received from work) and make sure you understand where certain amounts of money went and why, eg. laundry etc.
then read the attached information which came with your taxpack and go for it. Now the second copy of the tax return application is (according to my dad) a 'spare copy' or for you to use as your own personal records of your activity with the ATO.
Remember though, try to be thorough because you don't want to have to do it again if they find complications with your records etc.
enjoy
you'll be glad and proud when you receive your tax return
...even if it's just $22 *sniff sniff*