Solved Administrator updates windows 8

Hi I just installed 6 new Lenovo all-in-one desktops at a non profit center for Sailors. They all came with Windows 8 64bit operating system. Now I have to update them to Windows 8.1. As you know it takes a long time to do this through Windows store.Being a nonprofit the Internet is not the fastest because of money constraints.The first one took 5 hours.I have a windows 8.1 iso installation dvd. Can I use this to upgrade the rest of the machines or is this different than an upgrade disk.?
Please help

Hi, unfortunately to upgrade directly through windows 8 you will need to do it through the windows store which will require download. Contact the helpdesk and they may be able to suggest an alternative solution but unfortunately your windows 8 serial will not allow you to install a fresh copy of windows 8.1. Let me know how you get on. Maybe you could leave it on overnight?