From the Users screen you can use the checkboxes to select those users you want to remove access for.
You can also use the filter to identify groups of users you want to remove.
Once you have selected those users, hit the 'users selected' button near the bottom left of the screen. You will then see a list of the users you have selected and you can either go through and hit remove for them individually or use the remove all button to revoke access to your account or location.