How do I add an ISRC code onto an audio file?

I have searched for solutions and all of the solutions I can find involve options that do not exist on my fully paid for MP3tag software. For example there is no file/options on the main menu, which is a solution recommended on this forum.

Also can anybody tell me how to find the extended tag options? If I go to main menu "View" and click "Extended tags" I only get one dialogue box with limited options.

Last time I used this utility there was a way of cycling through several pages of additional tags for example "publisher" etc and I was able to add song lyrics. How do I find those extended tag editor pages please?

You can use the ISRC field name at Extended Tags. If you want to add the ISRC field to the Tag Panel or the File List, you can check

Thanks.

I want to try clicking Preferences - File list. Where do I find these options?

It’s probably Mp3tag → Settings... → File List on your system, or ⌘,