There's a few different creators who have made FT prefabs for Manuka, so you might have to be more specific on what you have/want
Pretty much all of them use some kind of patcher to add their own blendshapes onto the avatar, it's usually just a matter of making sure Manuka's FBX file is in the same place it originally was when importing the .unitypackage and then running their patcher tool
That usually makes a separate FBX, either in the creator's folder or Manuka's FBX folder, that you can then replace the Body mesh with, then add in a VRCFury or MA prefab to merge FX layers and menus to actually enable it
