Q:

Errors On Launching Browser And Going To Website (In Selenium Webdriver)

@alecxe - I have edited the code. But, I still get errors. Thanks very much for your help.
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I have done this several times before and it has worked. But for some reason, it is not working. I am using Microsoft Visual Studio 2015 (Community Edition - if that  helps. I have downloaded the necessary libraries and added the required dependencies in MS/Visual Studio. I have also added a picture of the error list.
Here is the code:
using OpenQA.Selenium.Firefox;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using NUnit.Framework;
using OpenQA.Selenium;
using OpenQA.Selenium.Firefox;
using System.Threading.Tasks;

namespace CV_Library_P.OM_09_2017
{
    class Valid_Username_Valid_Password
    {

        //Instantiate Firefox Driver
        var driver = new FirefoxDriver();

        FirefoxDriver.Navigate().GoToUrl("https://www.cv-library.co.uk/candidate/login");

        //Enter User Name - Email Address
        var user = driver.FindElement(By.Id("cand-login-left"));
        user.SendKeys("testsuccess761@gmail.com");

            //Enter Password - Account Pasword
            var pass = driver.FindElement(By.Id("cand-login-left"));
        pass.SendKeys("p@55word123!");

            //Click on Login button
            driver.FindElement(By.Id("cand-login-left")).Click();

A:

1:  Your first error says that: Invalid token class/interface/member declaration
Ans: You have missed basic concept of Encapsulation

You have not declared the main method.
Every code should be capsulated within the: Class--> Method-->Data

2: Error Method should have a return type.
This error occurs because you have not declared any method within your class.
3: If you are using Selenium 3.0 or greater version then you must have to initialize Firefox-Geckodriver path in your code. Check here, if don't know how to do this.
4: Instead of FirefoxDriver.Navigate().GoToUrl("") use:  
driver.get("Your AppURL")

