This article will take you through how to upload texts to be displayed in the Outlook add-in.
Go to the 'Libraries' on the Configuration panel and choose the 'Text elements' from the Asset libraries.
Then, either choose existing folder or create a new folder and press on Upload Files:
Once the file is uploaded, click on it.
If the document is intended to be used only for Outlook, then mark only Outlook.
Don't forget to save your actions!