Yeah as long as you have month and name selected then the code in the grey box will be all that you need.
If you already find some code in the htaccess file once you open it in notepad then you can add it after everything there. It may even be empty in which case you can paste it from the very first line.
It should work out hopefully. Also you may need to ensure that your upload settings in your ftp program are set to ASCII. It may be set as binary at the moment. Once you’ve dragged your edited htaccess file onto your server you can change the setting back to binary.
Two important things:
In notepad when you’re pasting the code make sure word wrap is set to off (Format > Word Wrap).
And of course when you save the file, make sure it doesn’t save as .txt. If it does you should be able to rename it later. But probably best to make sure it stays .htacess