If you have store with this values: {[text: 'Active', value: 1], [text: 'Inactive', value: 2]}
Set them using
Code:
{
	value: '1, 2',
	name: 'test',
	xtype: 'checkcombo',
	store: someStore,
	displayField: 'text',
	valueField: 'value'
}