Explanation
To add a Joblet to your Talend Job, you can use one of these options:
Type the Joblet name on the Studio canvas, then select it from the Palette drop-down menu. This will create a Joblet container on your canvas that contains all the components and links of your Joblet.
Drag the Joblet from Repository tree view to designer canvas. This will also create a Joblet container on your canvas that contains all components and links of your Joblet.
Drag Joblet from Palette to design workspace. This will open a dialog box where you can select an existing Joblet from Repository or create a new one.
You cannot use a tRunJob component and select Joblet from drop-down menu, nor right-click Joblet from Palette and select Add option. These methods are not available in Talend Studio and may cause errors or unexpected results. References: Talend Open Studio: Open-source ETL and Free Data Integration | Talend,
[Joblets - 7.3]