You have the ability to change between two resistance modes during a session: gear mode and ergo mode. To switch between the modes, press the action button (red button on the top) on the right shifter.
This is the default mode on your AtomX. Use the up and down buttons on the right shifter to change your gear. This mode feels like using the gears on a regular road bike.
In this mode, the AtomX will hold you to a specified target wattage, regardless of your cadence. Every structured training session on the AtomX uses ergo mode automatically to personalise each session to you and your fitness levels, your FTP, or your MMP.