How to execute a C# code in Unity 3D?

This is a simple question, but it is a bit hard for Unity newbie like me.

I have coded this. (See below.)

using UnityEngine;
using System.Collections;
using Mono.Data.Sqlite; 
using System.Data; 
using System;

public class NewBehaviourScript1 : MonoBehaviour {
    // Use this for initialization
    void Start () {

    string conn = "URI=file:" + Application.dataPath + "/sensor.sqlite"; //Path to database.
    IDbConnection dbconn;
    dbconn = (IDbConnection) new SqliteConnection(conn);
    dbconn.Open(); //Open connection to the database.
    IDbCommand dbcmd = dbconn.CreateCommand();

    string sqlQuery = "SELECT x1 " + "FROM sport";
    dbcmd.CommandText = sqlQuery;
    IDataReader reader = dbcmd.ExecuteReader();

    while (reader.Read())
    {
        int value = reader.GetInt32(0);
        string name = reader.GetString(1);
        int rand = reader.GetInt32(2);
    }

    reader.Close();
    reader = null;
    dbcmd.Dispose();
    dbcmd = null;
    dbconn.Close();
    dbconn = null;

}

}

and saved.

However, I do not know how to execute this. Any idea? Thank you.