I presume that you mean the "read more" link in the description is not shown in mobile view?
Use this code...
.sprocket-features.layout-slideshow .sprocket-features-desc {
display: block;
}
To create a custom CSS compatible with Gantry 5 please read this
http://docs.gantry.org/gantry5/tutorials/adding-a-custom-style-sheet
.
Remember to recompile CSS from base outline too.
Regards, Mark.