How can I get Ubuntu 16.04 to use my external monitor's native resolution?

My exteal monitor is an HDMI LCD screen with 2560x1440 resolution. My laptop is the "MSI GT72 2QE/Dragon Edition" listed on page two of https://www.msi.com/pic/faq/10015790...0001661_en.pdf, which is a document specifying the maximum exteal monitor resolutions for my system. My laptop screen is a 1080p LCD screen. I'm using the exteal monitor in a dual monitor set-up no problem, except that the exteal monitor is ruing at 1920x1080. It's doesn't look awful, but I really wanted to use its native resolution quality.

When I go to Displays in System Settings, 1080p is the highest resolution option available for my monitor. The exteal monitor is again a 2560x1440 Dell 27" LCD monitor. What can I do to fix this? Help would be uber appreciated