EPOS can be accessed from the back-office from the Multichannel menu, but if you don't have access to the back-office you can log directly into EPOS using a PIN number. On your main login page, click the "login to EPOS" link and enter your PIN number. You will be asked to select the till you are using, this will be remembered until you log out of EPOS. If you have not yet set up a default customer you will be asked to select one before you are able to use EPOS.
If you are only using one cash till but have multiple users working on it you can make use of the quick user change so that you are still able to monitor an individual's sales. To quickly switch user within EPOS click the Change user button, the new user can then enter their pin and continue to work. You may need to click the Home link at the bottom to see this screen: