Once you’ve imported an article, in the extension window you’ll see 3 options – Highlight OFF, Highlight ON and Highlight + Notes:
To make highlights and annotations you’ll need to have the Highlight + Notes option selected, then just drag your cursor across the section of text you want to highlight. You’ll see a little Sciwheel icon appear, just click it to select a highlight colour and add a note if desired. The Highlight OFF option will hide any highlights you’ve already made, and the Highlight ON option is for quickly making highlights without having to click the extra icon and add notes - with this option, any page you highlight will automatically be imported into your Sciwheel library.