Installation:
0) Steam users: verify your game's cache.
1) If you have an older version of "Magic Spells for Signs and Weapons" installed, delete the dlcAdtomes folder from your 'The Witcher 3 Wild Hunt\dlc\' directory and the Modadtomes folder from your 'The Witcher 3 Wild Hunt\mods\' directory. 
2) Extract the mod's archive to whatever folder you've downloaded it into.
3) Copy the 'bin', 'dlc' and 'mods' folders into your 'The Witcher 3 Wild Hunt' main directory.
4) Open Script Merger, refresh and re-merge any conflicting files.
5) Open inputsett.txt file and follow its instructions.
6) Run the game, go to the settings for this mod and set all three entries to default.
7) Play.