ember firebase pass models to action handler

I have ember data models hooked with firebase, characters and spells. I can create new models and save them to firebase. Now I wanted to add spells to character. I defined that character has many spells:

export default DS.Model.extend({
  chClass: DS.attr(),
  chName: DS.attr(),
  chImage: DS.attr(), 
  chSpells: DS.hasMany('spell', {async: true}),
});

In my hbs I listed spells in element, there is also input fields and add button.

Add new character <br>
name {{input value=mchName }}<br>
class {{input value=mchClass }}<br>
image {{input value=mchImage }}<br>

<br>
Choose Spells:<br>
<select name="spellslist" multiple>
{{#each spells as |spell index|}}
 <option value="{{index}}">{{spell.spName}}</option>
{{/each}}
</select>

<button {{action 'addChar' spells}}>add</button><br>

So when user types in character name, level and picks some spells I want to call addChar action function on add button and pass this data.

export default Ember.Controller.extend({
mchName:'',
mchClass:'',
mchImage:'',
store: Ember.inject.service(),

actions: {
addChar: function(model) {
  var newChar = this.store.createRecord('character');
  newChar.set("chName", this.mchName);
  newChar.set("chClass", this.mchClass);
  newChar.set("chImage", this.mchImage);
  newChar.get("chSpells").addObject(?????? how to get spell here ?????);

  newChar.save();

I know how to pass string from inputs, but I dont know how to pass selected spells to this function, its killing me.