There is a button labelled Add / Modify Watchlist on your Watchlist.
When you enter a stock name or symbol to add, the screen displays a list of possible matches below from which to select the exact stock. You have to select one of the matches for the system to know exactly which stock you're referring to.
Note: You may not see the drop-down list sometimes, because of the scroll bar on the right.
Learn to customize the Value Investing framework of Benjamin Graham, Warren Buffett's mentor.