The following article will guide you through the process of installing DarkRP on your Host Havoc Garry's Mod server.
Step 1: Log into your game control panel.
Step 2: Open the "Non-Workshop Mods" icon.
Step 3: Click 'Install' next to the DarkRP item.
Step 4: Allow the installer to complete.
Step 5: Navigate to the Commandline Manager (same area as the mod manager).
Step 6: Switch to the 'Custom Commandlines' tab.
Step 7: If you already have a Commandline created, edit it by clicking on it. Otherwise, click 'New'.
Step 8: Edit the game mode setting by setting the text box to "darkrp" (no "s).
Step 9: Save your Commandline and make sure it is selected by pressing the Select button on the right-hand side of the custom Commandline.
You're all set!