Hi there,
Welcome to SeaTheme forum.

Did you mean that the menu panel should slide from right instead of top on the mobile layout?

Regards!
SeaTheme – FAQs – WordPress Customization – Facebook

Thanks
Please paste the custom CSS code to “Appearance > Customize: Additional CSS”

.menu-panel  {  bottom:0;
    -webkit-transform: translateX(100%);
    -moz-transform: translateX(100%);
    -ms-transform: translateX(100%);
    transform: translateX(100%);

}
.show_mobile_menu:not(.navi-show-icon) .menu-panel,
.show_mobile_menu.ux-mobile.navi-show-icon .menu-panel { 
	animation: transX_100to0 .3s cubic-bezier(0, 0.99, 0.91, 0.99) both; 
}
body:not(.show_mobile_menu).hide_mobile_menu .menu-panel,
body:not(.show_popup).hide_popup .portfolio-panel {
	animation: transX0to_100 .3s linear both;
}
@keyframes transX0to_100 {
	0% {
		transform: translateX(0);
		position: absolute;
	}

	100% {
		transform: translateX(100%);
		position: relative;
	}
}
@keyframes transX_100to0 {
	0% {
		transform:  translateX(100%);
		position: absolute;
	}

	100% {
		transform: translateX(0);
		position: relative;
	}
}

Regards!
SeaTheme – FAQs – WordPress Customization – Facebook