Hello,
Complete instructions can be found here: https://cdn.eventideaudio.com/manuals/h90/1.9.7/content/h90-control/getting_started.html
Are you connected to your computer via USB? Have you added your device as outline in 10.2 Step 3? To update the pedal, click the cloud icon on the bottom right of the square that appears when you added your pedal. Click install on the top right.
