Hey Hayley,

Add this into the Custom CSS box located in your Salient Options panel (Make Sure there are no red cross in the Box) :

@media only screen and (max-width: 1000px) and (min-width: 1px) {
    #slide-out-widget-area .inner .off-canvas-menu-container li a {
        font-size: 22px !important;
        line-height: 26px!important;    
    }
}
@media only screen and (max-width: 690px) and (min-width: 1px) {
    #slide-out-widget-area .inner .off-canvas-menu-container li a {
        font-size: 18px !important;
        line-height: 22px!important;
    }
}

Thanks