Whether you can work out through Workit depends on your employer. You can easily check this with the employer check when you sign up: log in with your employer's code to see whether your organisation takes part and what your benefit is.
Is your employer not partnered yet, but would you like to work out through Workit? Tip your employer. And even without a partnered employer, you're welcome: you can take out an ambassador subscription (see What is an ambassador subscription?).