You can configure each email to be sent only when a condition is met as explained here. But you can also insert content to the email (like a specific text or image) conditionally. To do so follow these steps:
1.- Go to the email designer
2.- Click on “Condition”
3.- Define your condition (the content that you define will be added only when the condition is met). In the example below the content will be added only when the text box has the value of “Hello”
Editing your condition
If you later want to view or edit the condition that you specified you can click in the condition block and then on “Edit Condition”