[Koha] Unable to upload "koha-coverflow-plugin-v2.4.25"

Hi, I am using koha 18.11 running on ubuntu 16.04. I am trying to upload the plugin file "koha-coverflow-plugin-v2.4.25" and am receiving this error message "*Cannot unpack file to the plugins directory. Please verify that the Apache user can write to the plugins directory". * Please i need help. Thank you. Murphy Igbudu Systems Librarian University Library and Information Services, Benue State University Makurdi. Nigeria.