Hi shadow you do it bye finding the weapons you want to add then find the DE loot and put it to 1 example is below. DE Means dynamic event loot and is found in your types.xml
<type name="FAL">
<nominal>4</nominal>
<lifetime>7200</lifetime>
<restock>0</restock>
<min>1</min>
<quantmin>-1</quantmin> <quantmax>-1</quantmax>
<cost>100</cost>
<flags count_in_cargo="1" count_in_hoarder="1" count_in_map="1" count_in_player="1" crafted="0" deloot="1"/>
<category name="weapons"/> <usage name="Military"/>
<value name="Tier4"/>