Drag a window to the left edge of the screen to snap it there
Drag another window to the right edge of the screen to snap it there
Press Windows key + Left Arrow to move the active window to the left half
Press Windows key + Right Arrow to move the active window to the right half
Press Windows key + Up Arrow or Windows key + Down Arrow to resize or move the active window
Use Windows key + Z to open Snap Layouts
Select a split-screen layout from Snap Layouts
Choose the other open window to fill the remaining space
Drag the divider between windows to adjust the split size
Use Task View to open and arrange multiple windows side by side