How can I make Chrome my default browser?

Open the app drawer and drag the default browser icon toward the top of the screen and drop it on "App Info" - this should bring you to the Application Manager page for that app. On that screen tap "Clear defaults" - this should clear any settings that cause Android to use the stock browser by default. The next time you do something that tries to open a browser, you should be asked which of your installed browsers you want to use, and you'll have the option to make that the new default.