Note: You must use labels and the control must be first in markup. See example.
<form role="form">
    <div class="checkbox checkbox-styled">
      <input type="checkbox" name="sample" id="checkbox1" checked="checked">
      <label for="checkbox1">Checkbox - Checked</label>
    </div>
    <div class="checkbox checkbox-styled">
      <input type="checkbox" name="sample" id="checkbox2">
      <label for="checkbox2">Checkbox</label>
    </div>
  </form>

Disabled checkbox

<form role="form">
    <div class="checkbox checkbox-styled">
      <input type="checkbox" name="sample" id="checkbox1" checked="checked">
      <label for="checkbox1">Checkbox Disabled</label>
    </div>
    <div class="checkbox checkbox-styled">
      <input type="checkbox" name="sample" id="checkbox2">
      <label for="checkbox2">Checkbox Disabled &amp; Checked</label>
    </div>
  </form>