Selectors represent elements that share common characteristics. The easiest way to create them is by pressing the Show Selection button on the browser (if loading, selection mode will become active as soon as the page completes loading) and selecting one or more elements on the page. To select many elements, hold the control key while clicking on elements. Then, create a selector by right clicking Selectors and selecting Create from Selection.
To preview a selector, right click it and select Preview Selector in Browser. If not enough elements are selected, select some of the missing elements and then select Add Samples to Selector on the selector's context menu.
If creating a selector that selects a single element on a page, it's best to use samples from more than one page by first creating the selector with a single element in one page, then navigating to another page and adding another sample element from there.
To access a selector from a global, use the 'Select.' prefix.