I'm trying to install a Mod in TSL and the TSL Patcher says to place the spells.2da in the Overriade folder however I can't seem to find spells.2da in SWKotor2 folder. it seems to be non existent
The Spells.2da file has to be extracted with the KotOR Tool, under the Bif's > 2DA bif directory.
Perhaps it's in your mod's source file? Why don't you run a search for it in My Computer (assuming you have Windows)?