Boot Windows. Disable "fast boot", control panel > power options > choose what the power buttons do > change settings that are currently unavailable > un-check "turn on fast startup".
Open partition manager program, shrink windows partition.
Burn ubuntu server live on to a usb stick. Insert USB stick. Restart, press F7.
If USB stick does not show up, enter bios menu. Remove USB stick, wait a few seconds, then plug USB stick back in. Exit and reset bios.
Press F7, this time the USB option should show up.
Once in ubuntu, if the available disk space does not show as an available usable space, you can create with parted. Press F2 to open a new terminal. lsblk to show disks and partitions. parted /dev/MY_DISK to start parted. print free to show available space Start and End positions. (parted) mkpart primary ext4 START END to create the partition in a section of free space. quit and then exit to go back to primary terminal.
Select "[ Reset ]" at the bottom to load the new partition. Selct the new partition, then "Edit". "Format: ext4", "Mount: /", then save.
Rest of setup should work like normal.