OK - the correct answer is:
Go to a Google Now stock card
Click on the menu in the upper-right
Add or delete stocks to follow
Are you a finance guy or stock dealer? Well, Google has made following stock prices easier with Google Now Stock Card. You just need to add you stocks, and get updates from your stocks
To add or remove a stock from your list, follow this path:
1. Open Google Application
2. Go to Settings (you may press Menu Button first)
3. Tap My Stuff and then tap Stocks
4. Now Add or Remove stocks
If you have problem showing stock card, see: Google Now Not Showing Stock Cards