Assuming you already have a Google Analytics (GA) account, you need to create a new "property" for your account. Call it "Blogger: Name of your blog" or something like that. When you have been assigned a Tracking ID for this new property, you need to add this to your Blogger account.
With the latest version of Blogger adding your GA Tracking Code is very easy. Simply log in to your Blogger blog > go to Dashboard > Select "Settings" (at the bottom left) > Select "Other" > Scroll to the bottom and see the place where you put your Google Analytics code (e.g., UA-xxxxxxx-xx). Put just the Tracking ID number in; no quote marks or any Javascript is needed. > Click "Save Settings" at the top of the page. Google will do the rest.
Check GA in a week or so and see how much traffic is coming to your Blogger account.
