Hello,

First of all, enter the editing mode of the page where the Slider Revolution displayed. Check which one is used as shown here: http://prntscr.com/isshej

Then find this slider in Slider Revolution plugin as shown: http://prntscr.com/issi0h

Finally edit the height in the slider settings as shown here: http://prntscr.com/isyjfv

Here is the documentation: https://www.themepunch.com/revslider-doc/slider-revolution-documentation/ You will find all the instructions.

Best Regards