Gradient box behind text Montezuma theme

Hi – I’m using a child theme for the Montezuma theme and I’d like to add a gradient box similar to this other wordpress site:

https://attainiumcapital.com/

Is there a simple way to do this? Right now I just have a style code set up defining a background color – but is there a way to set a gradient with the style command?

Here is the site I’m working on

smartenergyboston.com

Thanks in advance