You'll need two programs to install this weapon skin. Make a copy of the files you'll edit in case there's a mistake.
MH2MDL Editor: https://www.dixmor-hospital.com/mods/view/manhunt-mdl-editor-2-0
MH2_TexEditor: https://www.dixmor-hospital.com/mods/view/manhunt-2-texture-tool
Installation:
Open MH2MDL Editor and open gmodelspc.mdl located in "Manhunt 2/global/"
Find the file named "MACE_CT" and click replace, then replace it for the file you downloaded.
Save and close the tool.
Open MH2 Tex Editor and open gmodelspc.tex
Click the option add, then select the textures in the textures folder (REMEMBER! Add. NOT REPLACE)
Save then select the weapon.
To select the mace you need PluginMH2 and Debug Menu by ermaccer.
And to use it in all levels you either need the Extended Executions mod or
All Weapons In All Levels MH2: https://www.dixmor-hospital.com/mods/view/manhunt-2-all-weapons-in-all-levels