If you DON'T have previous verion of the mod installed:
Copy DogCompanion.asi and the DogComapnion folder to your game main folder.

If you DO have previous version of the mod installed:
- Copy DogCompanion.asi to the game main folder.
- Replace only DogMeta.dat and Lang.dat in the DogComapnion folder.
- You may also replace DogComapnion.ini but you'll lose your custom settings. Therefore it's recommended to save a backup.