In order to templatize/parametrize an SSH connection field, click on a field that accepts data template injection (for example Commands) and and click on the Inject Template icon located next to that field. 
Not all fields have this icon, because not all fields can resolve injection values. An example is highlighted below.
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When selected, the following template selection popup appears:
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Select the Data Template and field of choice and click on Inject. This will templatize the selected field.