a network-related instance-specific error occurred while est

a network-related 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 configuered to allow remote connection(provider:SQL Network Interfaces,error:26-Error Locating Server/Instatnce Specified)(Microsoft SQL Server)

 

  I am trying to start service but goes to failed and if trying for SQL server Agent(NANDKISHOR) there is no option to start or any other bcoz its disabled 

 

 

 

pls help me to solve this problem