Add it to your server
In your server's .ini file (servertest.ini by default), add these to the existing WorkshopItems= and Mods= lines, separated by a semicolon (;).
WorkshopItems=3619862853;3827827224
Mods=ZombieBuddy;SaveSlots
These lines include the mod it requires, as its Steam page declares it:
- ZombieBuddy ·
ZombieBuddy
| Workshop item | Subscribers | Declared in |
|---|---|---|
| Save Slots [B42]3827827224 | 53 | description footer |