Hi Kariocecus,
Go to your Articles container, choose "advanced settings" tab, click "latest post" tab on the left.
Here you see your "latest article chunk".
Go to this chunk and edit
Use
in your template to show these introtexts.
Tip: However you also could use:
[[+introtext:default=`[[+content:ellipsis=`250`]]`]]
which enables "introtext" but uses first 250 chars of the "content" if "introtext" is not set
