I used to use \"+y to copy text to system\'s clipboard, but it doesn\'t work in vim of Bash on Windows.
To copy to the clipboard from within vim in Bash on Windows 10, hold Shift and drag the cursor over text. then press enter
A selection should look like this before pressing enter:
EDIT: This only works with text that fits on the screen all at once; it cannot be used to copy blocks of text that span many 'screens'