Little push whit a addon

Hello,
I’m totally green whit addons. And i’m looking for a little push in right direction. Maybe I should tell you what i’m trying to achieve.
The addon after pressing a button should copy a text from few places of a web website.
And after going to a other site pass it to a form after pressing second button.
I install mozilla SDK jetpack. Can you direct me what to read or if you’ll be so kind just mention a function whit i can use? looking forward for your replay

You’ll want to look into modifying web pages and possibly using the clipboard.

Thanks man it helped me alot. specialy the article about jQuary implementation