You don't. Upgrading the internal drive of the Xbox One is not supported by Microsoft and messing with it will void your warranty. It's not impossible to do but it involves a good deal of hackery.
The good news is, you don't need to upgrade your internal drive since the Xbox One supports external drives. You can use any USB 3.0 drive that holds at least 2 GB of data. I have a 4 TB WD MyBook that I'm using; it costs about $115, works great, and I have tons of space available.
True performance junkies might want to look at 7200 RPM external drives but I've never seen evidence that they offer a major decrease in load times. In my opinion you're better off with more storage than a slightly faster drive.
You should know that the drive you used will be formatted for use with the Xbox One; any existing data on the drive will be lost.
While it may void the warranty, the warranty is only a 1 yr warranty, so at worst, one must wait 1 yr from the date of purchase to upgrade the internal drive.
While using an external drive will work for many, it doesn't provide the same benefits replacing the internal drive does. The internal drive should only be replaced with an SSHD or SSD, however you only gain 1 - 2 seconds of load time by going with an SSD over an SSHD. Plain mechanical HDDs (7200RPM) take an additional 60 - 75% longer to load from a cold boot on the Xbox One, with SSHD/SSD loading in ~30 seconds (games also load faster with SSHD/SSDs, with SSDs only offering the same 1 - 2 second(s) gain over SSHDs, and mechanical HDDs taking substantially longer).
7200RPM drives do allow for faster data access, but provide little benefit when installed in an Xbox or other game system, and would cause more problems than they solve due to the massive amount of heat they give off in comparison to 5400 RPM drives. Because of the intelligent way SSHDs cache data, they're the best of both worlds, providing SSD like speed and performance for the same price range as a purely mechanical drive. SSDs are more than worth it in laptops, desktops, and servers, but not so much in game systems.
To add to @Sveta's reply, another great tutorial with the required scripts can be found: