You're entitled to it if you have a child under 6. It's called the UCB (Universal Childcare Benefit). It's $100 per child under 6. It's taxable income, however, so at the end of the year when you file your taxes it has to be declared... although it can be declared on whoever's income is lowest. So although the wife may be receiving the benefit in her name, if her income is higher than her husband's, it would be declared on his tax return.
If you were already receiving the Canada Child Tax Benefit (which is based on income) then you would have received it automatically. You should have been given a CCTB application by the hospital when your child was born. You also "re-apply" for the CCTB when you file your taxes because the amount of CCTB received is based on your declared income of the previous year. So your tax return for 2005 will determine your monthly CCTB amount from July 2006 until June 2007.
The first cheque for the UCB was in July and was mailed, even if you were receiving the CCTB directly into your bank account. Along with the first cheque is a form to request that the UCB be directly deposited. If you weren't receiving CCTB (because you had forgotten to file your taxes, or didn't apply for it once your children were born, or were making too much to be eligible for it) then you just make an application for the CCTB and although you may not be eligible for CCTB you'll receive the UCB if your child is under 6.