If you know nothing of SourcePawn, you must start by learning by reading the following links:

Introduction to SourcePawn scripting:

http://wiki.alliedmods.net/Category:SourceMod_Scripting

Full Pawn documentation:

http://www.compuphase.com/pawn/Pawn_Language_Guide.pdf

Sourcemod Function reference:

http://docs.sourcemod.net/api/