Hi ddzarrro,
Here is a link to a screen flow tutorial I just created for you.
how to create email template in Mautic v2.5.1
It shows the steps to create an email template in Mautic V2.5.1 (which is more or less the same for most Mautic Version 2.x.x)
The editing is a bit crappy, but you can see the steps needed.
Cheers
Ray