In v3.0, you can add a new stock by selecting the watchlist(s) that you want to add to and typing in the symbol or company name into the search field at the top of the screen.
As you type, a list of suggestions will appear below the search bar. Press the enter key to select the top suggestion or use your mouse to hover down the list and click on a different suggestion.
If there are "No Results" that means no supported symbol was found. Check your spelling, and try to enter just a portion of the name. Many times, specific mutual funds can be found by narrowing down the list of "Blackwell" funds to the one you are looking for.