Right click, add pages to Pinboard.in
The whole point of this extension is to get out of your way. Find an awesome link via Twitter? Open it, right click, post it, close it. The first time you post a link to Pinboard (http://pinboard.in/), you'll be prompted to input your login information, and set up some sane defaults you want Instapinboard to use whenever you post a link. Want to be a proper taxonomist? That's great, just log into Pinboard and on your own--this extension is for people who just want to remember lots of sites, and not distract themselves from the task at hand.
Login information is stored using Web Storage inside your browser, and is not stored anywhere else, nor passed to any other site, except Pinboard.