Add component to fire event (checkbox (1) in example below):

Adding Lightning Component to the form

Below test event is named "invoke"and has "displayComponent" attribute which will pass TRUE of FALSE to the lightning component.

<aura:event type="APPLICATION" access="global">
    <aura:attribute name="displayComponent" type="String" access="global"/>
</aura:event>

Below handler and attribute are added to component:  

 <aura:handler event="c:invoke" action="{!c.toggleVisibility}"/>

 <aura:attribute name="display" type="String"/>

Component UI will be displayed on the form if 'display' attribute is set to TRUE:

 <aura:if isTrue="{!v.display == 'TRUE'}"> 
 ... 
 ... 
 
 </aura:if>

toggleVisibility function added to component controller updates 'display' attribute with event 'displayComponent' parameter:

toggleVisibility : function(component, event, helper) {
   component.set("v.display", event.getParam("displayComponent"));
}

• Populate "Name" field (2) with event name using c:eventName if your organization doesn't have namespace, and namespace:eventName if it does.
• To pass parameters (3) to application event use event attribute name as a parameter name:

Below is setup of two onChange events tied to the checkbox component.

First event (4) will be fired when checkbox is checked (see event conditions on the screenshot below) and will pass TRUE to the lightning event - this will display lightning component UI on the form.

Second event (5) will be fired when checkbox is unchecked (see event conditions on the screenshot below) and will pass FALSE to the lightning event - this will hide lightning component UI on the form.