FiveM
Copy gta5interiors_splitsides folder to your resource one located on the server.
Add start to server.cfg.
RageMP
Copy the gta5interiors_splitsides folder into “server-files/client_packages/dlcpacks”
Singelplayer
Copy the RageMP/gta5interiors_splitsides folder into “mods/update/x64/dlcpacks”.
Add “dlcpacks:/gta5interiors_splitsides/” to your dlclist.xml.
Credits:
GTA 5 Interiors