Open the scenario PediaIcons.txt

A little more than a third way down find the section:

#start units
Go to the end of that section (about half way down the file).

Add details of your new unit:

#ICON_PRTO_Malaria
art\civilopedia\icons\units\MalariaLarge.pcx
art\civilopedia\icons\units\MalariaSmall.pcx
Now, move to almost the bottom of the PediaIcon page to the section:
 
####
# Unit animations

Go to the end of that section.
Add details of your new unit:

#ANIMNAME_PRTO_Malaria
Malaria

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