Thanks for downloadin Undead Valentine. Please make sure you have Map Editor 0.7.0.0 installed, a link to download this is below.

To Use: 

1. Download map editor here, https://www.mediafire.com/file/oxytuxdgjlid5xj/MapEditor_0_7_0_0.rar/file
2. Put UndeadValentine.xml into, C:\Program Files\Rockstar Games\Red Dead Redemption 2\MapEditor
3. Press F4 and load the map file.

RECOMMENDED MODS
Undead Nightmare Camps
Undead Black Water
Undead Towns - This map was built on top of Valentine with this mod installed, it shouldn't be necessary but it will look as advertised with this mod.
Undead Nightmare II - Origins - What's the point without this mod? The weather effects in the screenshots are from this mod.