Try to think in terms of a model and what happens to that model when a checkbox is checked.
Assuming that each checkbox is bound to a field on the model with ng-model then the property on the model is changed whenever a checkbox is clicked:
<input type='checkbox' ng-model='fooSelected' />
<input type='checkbox' ng-model='baaSelected' />
and in the controller:
$scope.fooSelected = false;
$scope.baaSelected = false;
The next button should only be available under certain circumstances so add the ng-disabled
directive to the button:
<button type='button' ng-disabled='nextButtonDisabled'></button>
Now the next button should only be available when either fooSelected is true or baaSelected is true and we need to watch any changes to these fields to make sure that the next button is made available or not:
$scope.nextButtonDisabled = !$scope.fooSelected && !scope.baaSelected;
}, true );
The above assumes that there are only a few checkboxes that affect the availability of the next button but it could be easily changed to work with a larger number of checkboxes and use $watchCollection to check for changes.