Difficult to say without seeing your Brush panel. As your layers are set, the Splatter brush will only show where it overlaps the text, which I'm guessing you have right.
If the brush preset does not already have Build-up checked, do so. That will make it continue to lay down as long as the mouse button is pressed (or pen in contact with the tablet)
I think you already have Color Dynamics checked, but we'd need to see the contents. You also need the foreground and background colours to be something other than black and white to make the most of that, but I think you already have that right.
Splatter brushes can splash your images with bloody strains, paint splash. Sometimes is can just act as a stamp tool but with the Photoshop tool you can still add stroke width, spread etc to create a much realistic stamping of the brush. These brushes are in Photoshop .abr format and will work only with Adobe Photoshop software.
Your splatter brushes will not be visible outer clip mask area. Just release the clip mask layer above the text and see and there will be lot of paints. Whatever you paint in the edges of the text outer on clip mask layer will not be visible outer mask area.
Could you please post a meaningful screenshot with the pertinent Panels (Layers, Channels, Options Bar, …) visible?