The PartTools package is a set of utilities used by modders to import 3D models into KSP. PartTools also includes the coloranimation tool and the KSPAssetCompiler tool (for compiling asset bundles).
PartTools have been updated and re-compiled for Unity 2017.1.3p1 for KSP 1.4.0/1 to include all of these tools in one unity asset bundle and font asset bundle capability has been added for Localization.
  It can be downloaded here.

To install:
Import the custom bundle in the zip file into your Unity project.

For information about how to build and use fonts for Localization please refer to this link.