Not writeable

“Writeable” talks about the permissions set You can change the permissions via FTP to 666 so that wordpress can write to the .htaccess file, or take the code that you are given when you change the permalink structure and paste it into the .htaccess file.

Although if your permissions are 444, you’ll have to change them anyway because you won’t be able to write to it either.

https://codex.www.ads-software.com/Using_Permalinks

Ok. I assume you mean the permissions are actually set in .htaccess?
Will this also enable me to edit say, the footer of the blog?

Have a look at Changing_File_Permissions.

File permissions are not set in .htaccess. But .htaccess has to have proper permissions for WordPress to automatically update it when changing Permalinks.