If there is one thing you're waiting on, you don't need a monitor for the whole shop. Paste the product's link and StockWatch watches that one page.
You'll hear when it comes back in stock and when its price drops. If you haven't set up any alerts yet, they go to the email address you signed up with until you change that in Settings.
Watches have a list of their own and don't appear among your monitors. Open Products and switch on Watched, or press the Watched items row on the Monitors page.
A watch doesn't use up one of your plan's monitors. The number of products you can watch at once is 15 on Free, 150 on Standard and unlimited on Power User.
Press History on a watched product to open it.
If one of your monitors covers a whole shop, you can still single out a product. On Products, press the bell on its card. A sold-out product has a Notify on restock button that does the same thing. A watched product gets through even when the monitor's keywords would have left it out.
Make sure the link goes to one product, and not to a category or a page of search results. If it still can't be read, the box offers other ways in:
If a shop comes with a higher plan than yours, the box offers the upgrade, or watching the page from your own browser. Pokemon Center product pages can't be watched one by one, so for those it offers queue alerts.