Do I Install Tape or Valve First on a Tubeless Rim
Having looked a bit closer, I see these are tubeless specific road wheels. These shouldn't need a rim tape at all.

Just, make sure no rim tape ist mounted, stick the valve in, screw it on and mount your tires.

PS. This has complete instructions on page 10.
http://www.dtswiss.com/Resources/Support/WHEELS/WHEELS-User-Manual.pdf