Flex-6000 transceivers can directly transmit CW, so on the CW tab of WinWarbler's Configuration window,
set the Xcvr mode selector to CW
set the CW offset (hz) to 0 (or leave the box empty)
set the Default TxPwr to the power (in watts) you'll use when operating in CW
check the display xmit/rcv characters box
in the Keyboard mode panel
uncheck the auto start and auto stop boxes (explore these later)
select character (if you are using an amplifier, word is more appropriate)
set the Keying panel to Xcvr Ctrl App
Sending speed can be controlled via the WPM selector on WinWarbler's Main window, or via SmartSDR's Speed slider.
More Flex DX Lab configuration here....
The keying panel is in the lower left corner of your CW configuration screen. It is in purple letters. It is located under PTT.
You will also need to configure DX Labs Commander to control the Flex radio. See the documentation Iink I sent to you. It is under Connections and Applications at the top of the page. This will allow DX Labs software applications talk to your radio.