Use an Ethernet cable directly from your modem/router to your xbox one because the wireless card in xboxone is terrible. That is about all you can do, the microsoft servers for game updates are slow as well.
1. Make sure your Xbox one is wired to the router or modem with Cat 5e or better cable
2. Buy high speed of 200Mbs or greater download speed
3. Make sure other devices on your local network aren't using a lot of bandwidth
4. The game update is 16gig so if you don't have a 300mbs speed or higher download speed, it's gonna take a while
5. Run a detailed report using the Xbox one NAT settings to make sure you have no packet loss and check the download and upload speeds after its done. Comment here with those and we can help suggest how long it'll take
Yup...I get 10-15 Mb/s out of my crap ISP with a wired connection, took about 5 hours for me. If I hadnt plugged it in (I normally dont have it wired) I get about 2-3 Mb/s down - would have taken much longer. I imagine most people get more out of their ISP though so wired is definitely a must for big files like this.