MS 2008 c# SQL remote server

Question

How to configure SQL Server 2008 to allow network connections

im getting this error when someone else runs my exe on there computer, on my computer its working find.

A network related or instance specific error occurred, while establishing a connection to SQL Server.
The server was not found or was not accessible. Verify that the instance name is correct and that
SQL server is configured to allow remote connections.(provider: SQL Network Inrerfaces, error:26 -
Error Locating Server/Insatance Specified)(Microsoft SQL Server)