To start, you'll need to click on the sponsored link window displaying the Yahoo "Y" and then wait for the window to load (it might take a bit longer than normal, as the promotion has to decide which browser you're using to access it). From there, you're given instructions on how to make Yahoo! your homepage on that particular browser, but at the bottom of the window sits a countdown timer that starts at 30 seconds and slowly counts down (much more slowly than 30 seconds, that is). When it finally does run out, you can click on the "Finish" button to end the promotion and receive your two Farm Cash.
As usual, your Farm Cash should automatically update into your account upon closing this activity window, but if it doesn't, a simple refresh of the game should do the trick. Either way, make sure to complete this activity the very first time you see it appear under your FarmVille gameplay area, as these cross-promotions tend to be incredibly fast-moving, and may disappear even after refreshing the page.
Were you able to earn your free Farm Cash from Yahoo, or has the promotion not appeared for you yet? Sound off in the comments.