访问Wordpress functions.php

So the title is pretty self-explanatory. I need to access functions.php in wordpress because Wordpress is adding random p and br tags and it's messing up my code. Searched for over an hour and nothing worked:

What I have tried:
1) Connecting via FTP (which isn't viable, long story)
2) Going to Appearance > Editor, which isn't showing. I have searched this issue up as well, and the only solution seems to be deactivating plugins, which I have tried.
3) deleting all my code, then pasting it all in
4) Ctrl + f5
5) deleting some of my code, then pasting it again

Websites I've looked at:
https://www.converticacommerce.com/support-maintenance/how-to-edit-functions-php-in-wordpress/
https://www.webnots.com/how-to-edit-functions-php-file-and-add-new-functions-in-wordpress/
https://www.nosegraze.com/edit-functions-php/

All these websites suggest the first two things in the What I have tried list.

If there is another way to stop the p tags, please tell me

I understand that you are having issues in accessing your theme's functions.php and not with the code. Write a new plugin (code below) and upload to 'wp-content/plugins' directory and activate it. That's it!

<?php
/*
Plugin Name: Implement wpautop
Version: 1.0.0
Description: Implement wpautop function.
*/

remove_filter( 'the_content', 'wpautop' );
remove_filter( 'the_excerpt', 'wpautop' );