How do I add non WP code?

Hi,

I’m having a miserable time trying to work out how to add the code for a advertising block.

My understanding of the basics is limited to put it mildly, although I’m learning. I’ve worked out (rightly or wrongly) that I need to put in in admin and then either the theme editor or sidebar? I’ve tried with both and nothing.

The organization that produces the scripts doesn’t give instructions.

Do I need to upload to the server and if so could somebody please tell me how I can do it.

Thanks for any help,

Mike