Change WordPress URL in General > Settings

I installed an SSL plugin that crashed my site. Per the instructions, I had to add the following code to the wp-config.php file:

define( 'WP_HOME', 'https://example.com');

define( 'WP_SITEURL', 'https://example.com');

I got the site back working but now I’m unable to change the site URL in General > Settings. I tried removing the code above once the site was fixed but that crashed the site again. How can I change the setting so that I can edit the WordPress URL in General > Settings?

I have tried adding

update_option( 'siteurl', 'https://example.com');

update_option( 'home', 'https://example.com');

to the functions.php file but when I try to open it the file opens MAMP Pro because the site is locally hosting while I’m building it. I have no idea where to go from there to add the previous code into the fucntions.php file. Please help. Thank you.