.htaccess File is being Ignored

Question

I have been following this tutorial for setting up my htaccess file. Mainly for SSL reasons and error document reasons

1. First issue is this apache2 location:

---

sudo nano /etc/apache2/sites-available/default

---

When I use the above filepath it takes me to an empty file. However I figured that it is referring to my Apache2 config file, which is:

---

/etc/apache2/apache2.conf

---

Correct me if I'm wrong though.

2. Secondly, within this file, the tutorial (and many other tutorials) are pointing me a directory. Once the directory is edited, it should look like this:
   <Directory /var/www/> Options Indexes FollowSymLinks MultiViews AllowOverride All Order allow,deny allow from all </Directory>
   However, my directory is not like this. This is mine:
   

<Directory /var/www/SalesChecker> Options Indexes FollowSymLinks AllowOverride None Require all granted </Directory>
When I try to edit my own directory in any way, it seems to break the apache server and then I am unable to view any of my files from a browser. Also, why is my directory so dissimilar to the example's?

My .htaccess file has an error 404 ready to go, but when a user enters an incorrect URL on my server, my error page is ignored (which isn't surprising considering I know that Apache isn't overriding All)

Does anyone have any suggestions or ideas? Is my logic correct here? Am I looking in the wrong Apache folder? Or why when I try to edit my directory it breaks the website?

My .htaccess file is in my main website folder.

I'm a newbie to Apache and Linux work in general so any suggestions at all that would improve my knowledge would be appreciated.

Thanks!