Once you have linked your ISC account, you do not need to 'sync' your posts as such. You need not add any URLs at all. It was just a suggestion if you wish to know which section is getting you any earnings.
Regarding your query "I should add the url of different sections, but of my threads only right?"
- If at all you do add the URLs, you can either add the section's URL and/or individual page URLs (e.g. a forum thread which you posted or one in which you responded; an Ask Expert query you asked or one which you answered; an article you submitted, etc.) So, yes, you can add URLs of a school or job post as well. It is all up to you! You can add up to 500 maximum URLs as "channels" in your AdSense account.
Regarding your query "I'm allowed to edit and type for my blog, can I do the same for the ISC urls that I add too?"
- I am not sure what you are asking here. While a blog URL can be edited by you at any time, you cannot change the URL of an ISC post submitted by you. An exception is when you write an article, then change the title - you can then inform the editor who will do the needful to ensure that the URL which appears in the browser then matches your article's new title. So also with a school post or job post - if you have made some spelling error in the title, say, you can inform the editor.
If you are asking about removing URLs from your list of channels in your AdSense account, then, yes, this you can do by simply ticking the box next to the URL and selecting 'remove' from the drop-down list at the top.
When people come at you with their worst, you should come at them with your best (advice given to Selena Gomez by her mother, quoted in Time magazine.)