seagate personal cloud 5tb plex app question



Hello , Totall newbie to servers got this as a Christmas present spent hours doing battle eventually managed to fathom out how to get some photos , some music onto the 5tb personal cloud , added apps including plex , it played up so I reinstalled it and this time it worked ok, however I was concerned about login on my device tried firefox and ie browsers firefox informed me the login was unsecure instead of green ok site safe padlock had red line , I found there was an update for plex but hadn't a clue how to update the app on the server itself, if I logged in to plex via the pc green padlock was there so I knew it was secure , why should the plex app which id installed on the Seagate login be unsafe youd think it would log in to safe secure link sorry for being thick but how do I fix this...I want my server to be secure obviously before I put personal stuff on it , can anyone kindly advise me how to firstly solve the login to plex issue and how to update to latest version of the plex aim is to use plex in conjuction with amazon echo to play music around the house via voice search ....but until I get this sorted I cant get any further