Hi Anita, what are you referring to: a 401(k), an investment account or a particular mutual fund?
It would depend on what fund balance you are referring to. An investment account and a 401k account will have a link for you to establish an online account access- similar to your banking accounts.
Just about all custodians (institutions that hold your money) have access to a website where you can check your balance and send statements (either paper or digital) so you can get regular updates on your fund balance. Go to the website of the company that holds your account to learn how to access both.