Code:

string accessPath = Application.StartupPath.ToString() + "/dbService.mdb";

string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source" + accessPath;

OleDbConnection dbConnection = new OleDbConnection(connectionString);
string commandSqlString = "INSERT INTO Client VALUES ('" + clientName + "');";
OleDbCommand dbCommand = new OleDbCommand(commandSqlString, dbConnection);

dbConnection.Open();
dbCommand.ExecuteNonQuery();
dbConnection.Close();