hi, i have create users and rolls and all thing work very good on my computer but after upload view exception

Code:
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 Interfaces, error: 26 - Error Locating Server/Instance Specified)
how can i change connection string for mdf database

pleeease help me
with my regards
thanks in advance