I'm assuming by "change the text" you mean the font, size, or color.
In order to change it, you first need to know what it is. You can do this by right clicking it and clicking "inspect element" to find out whether it's an H1, H2, etc... My guess is that it's an H1.
Once you know what it is, you need to go to your custom CSS in Deco and type in something like this:
Adding this will change ALL of the H1s on your website. If you only want certain H1s to change, you'd need to be specific in your CSS reference. For example, including an id (#home_index) before the H1.
Hope this helped.
It occurred to me that by "change the text" you might also just mean changing what it says.
To do this you also need to know what it is and very specifically how to reference it.
The text you highlight in your attachment is actually an image. Specifically it can be disabled or replaced by navigating to Website Pages and configuring the Page image widget on your hope page or other system pages like Create, Products etc.
Thank JimUMFan for jumping in with more advanced options for text changes.