ARIA. Need to use ARIA-EXPANDED with ARIA-HIDDEN?

I am new to cast ARIA. If I have a function like a tooltip, that is, if someone clicked the question button, more text will appear that describes in detail the instructions for filling out the form field, should I use an attribute with the aria extension, a hidden attribute, or both?

<div class="login-form-field tt-highlight">
    <div class="error-message error-style">
        <p>Sorry you have not entered anything in the field above.</p>
    </div>
    <div class="col-xs-10 col-sm-10 col-md-10"> 
        <label for="inputTxtCustomerPostcode" class="login" />Postcode:</label>
        <input id="inputTxtCustomerPostcode" type="text" />
    </div>
    <div class="col-xs-2 col-sm-2 col-md-2">
        <a title="Please enter a valid case reference tooltip" class="login-tooltip" data-toggle="collapse" data-parent="#accordion" href="#collapseTxtCustomerPostcode" role="button" aria-pressed="false"></a>
    </div>

    <div id="collapseTxtCustomerPostcode" class="panel-collapse collapse" role="tree tooltip">
        <div class="panel-body" role="treeitem" aria-expanded="false" aria-hidden="true">
            <p>some text goes here for the tooltip</p>
        </div>
    </div>
</div>