The calculation on schedule 6 will decide how much benefit you can get. Most people are eligible to apply unless in some situations like being in prison or going to school full-time for more than 3 months while having no child. See CRA guide here.
However, CWB is designed for families with very low income, mainly to offset the welfare claw-backs caused by working income. So the result for most people will be zero unless you have very low income.
We recommend you always apply for the CWB if eligible and let the software calculate how much you can get.