Mods>update>update.rpf>common>data

(Look to the right) 

Hit "edit mode in top right"

Right click on dlc list select edit and add this line after recent pack. 

<Item>dlcpacks:/katana/</Item>

example: 

<Item>dlcpacks:/addonprops/</Item>
<Item>dlcpacks:/custom_maps/</Item>
<Item>dlcpacks:/katana/</Item>
</Paths>	
</SMandatoryPacksData>

click "save"

And your done! Spawn via trainer with:

WEAPON_KATANA

(If you have simple tainer you can add it into added weapons list for quick access)

Extra Info: 
I did not make this model all credit goes to these authors below, I simply edited the holster animations and big thanks for allowing this to be an addon weapon! 

Model converted to grand theft auto V by: Sandra Linson
Model created by: BlackBradHz 
https://el.gta5-mods.com/weapons/katana-sword-highpoly-4k
Database created by: yeahhmonkey 
https://el.gta5-mods.com/tools/add-on-melee-weapon-base (no longer available)
