//Use the FundInstructions_Settle method
var client = new BFSServiceReference.bfsapiSoapClient();

var credentials = new BFSServiceReference.Credentials()
{
    UserName = bfsusername, //Username of administrative user in your instance of BFS
    Password = bfspassword, //Password of the administrative user in your instance of BFS
};

var target = client.FundInstruction_Settle(new BFSServiceReference.FundInstructions_SettleRequest()
{
    Credentials = credentials,

    identify = bfsidentifier, //Identifier is a unique token for your instance of BFS 

    ActionTriggerDataEntity = new FundInstructions_Settle()
    {
        BrickId = new Guid("488c39eb-07b8-4998-8d24-a088b9905484"),
        SettlementDate = DateTime.Parse("2016-05-01"),
        ValueDate = DateTime.Parse("2016-05-01"),
        SettledAmount = 100M
    }

});

Console.WriteLine(target.Message);