You will find Actions panel in both 3D and 2D Tabs. This means that you can create and edit events while working on 3d objets or 2d layout.
Actions in Webseed Studio is a target/trigger system.
Actions are organized in Events. Each event contains one or several targets and sub targets for scenarii.
An event controls the trigger's behaviour and the target's action.
To create a event, click on "Event+" button.

An Event 1 dialogue box appears. It contains 2 lines : Trigger (top line); Target (bottom line).

You can open and close the Event box by single clicking on the blue arrow on the left, or on the white bar.
Rename the Event by double clicking on the name; the name is highlighted in blue so you can change it.
If you want to delete the Event, just click on the Minus button on the right of the title bar.

You have your first event. What do you do now?

Click on the Trigger and chose the component that will become the trigger for your event.
You can also type the name of a component in the Search field to select it easily.
For the moment, only 2D components can carry a Trigger behaviour.

Next, click on the Behaviour next to the trigger. The behaviour is the way the trigger acts with the mouse pointer dependind on its position (click, over or out).

Bottom line (target).
Click on Target and chose the target as you did for trigger.
You have several categories for triggers. You can create interactivity with all types of objects and components in Webseed Studio. You also find an Extras category with Timer (waiting function) and Navigation (to do navigation buttons in Applets).

Each target type is associated with a specific behaviour.
Webseed Studio automatically proposes target's behaviours according to your target in the dedicated button

Finally, open the Options menu to adjust the last parameters.

As seen below, you can create as many targets as you wish for one trigger.
On clicking the trigger all actions's targets run simultaneously.

TIPS
Add a Target	To add a new Target to an existing trigger simply click on the + icon on the left of the last Target at the bottom of the Event box
Delete a Target	To delete a Target, click on the - button on the right of the Target line.
	If the name in the buttons fields is too long does not fully appear, just slide your mouse over it and a tooltip appears with the complete name

Webseed Studio can go further than the Target/Trigger system with the Scenario.
Scenario gives you possibility to run targets in succession
Regular Targets are displayed in blue and Scenarii Targets in purple.
To create a Scenario Target, click on the small + at the bottom left of the Target line.

In the example below, the first target commands the opacity (set opacity) of the image called "Image Dimension". This image goes from 0 to 90% of opacity in 50 frames
When this regular action is finished, a first Scenario target plays a "Webseed Timer" used for waiting. It waits a 100 frame period.
At the end of this waiting period, a second Scenario Target launch another "set opacity" on the same image that goes from 90 to 0% of opacity in 30 frames

Thanks to multiple targets types and to all the behaviours and options integrated in Action panel, you have at your disposal a tool which can help you create a very large number of interactivities.