[Koha] Including Login to access the OPAC

Dear Colleagues, I would like to make my koha library catalogue accessible over the internet but at the same time I would like to secure it such that only authorised persons can search and use the catalogue. I specifically would like that when a user accesses the catalogue they initially receive a login screen just as is the case with the staff interface. Could anyone kindly guide me on how I may achieve this. Hope to hear from you. Anselm Olweny Teaching Assistant East African School of Library and Information Science Makerere University Kampala, Uganda