As mentioned before, in order to edit a Component Definition you can open WorkWithPlus for Web Settings > Component Section and select the Component to edit.
Also, if you are in an instance where you added a Component, you can make right click over the Component > Open Component Definition:
In the Component you can edit the instance, and also add Event Blocks. As for the instance, any control can be added and in the same way as you work in an instance:
Then, you need to configure which properties this component will ask the developer to fulfill at the moment of adding it in some instance. In order to do this, each node has a property named 'Editable Properties':