You get the tracking code by signing up on Mouseflow.com. You can easily create an account for free by following this link: https://mouseflow.com/sign-up/
The code is not working
Make sure you've inserted the script code in the settings page.
Check that you have the wp_footer() function in the blog template.
Check your blog's html source (Page / View source) and search for "mouseflow". In case the script found at the end of the section, but still not working, you're probably running the site from a different domain than the one you entered on your mouseflow account. Make sure that the domains are matching.