Raising at a No Limit (NL) or Pot Limit (PL) table can be done using the popup slider that appears next to the action buttons.
The slider appears automatically at the moment when you need to make a decision. You can drag the slider to the position corresponding to the desired bet size, or use the scroll on your mouse to change the position of the slider.
Next to the slider, you will see the bet size, which will change depending on the position of the slider. If the previous table bet was $30 and your slider is set to $100, then you will raise to $100.