Place the following code into your style.css file. Place any ipad or iphone specific styling between the brackets.

/* iPads (landscape) ———– */
@media screen and (min-width : 768px) and (max-width : 1024px) and (orientation : landscape) {
/* Styles */
}

/* iPads (portrait) ———– */
@media screen and (min-width : 768px) and (max-width : 1024px) and (orientation : portrait) {
/* Styles */
}

/* Smartphones (landscape new phones/tablets) ———– */
@media screen and (min-width : 501px) and (max-width : 767px) {
/* Styles */
}

/* Smartphones (landscape iphone 3/4) ———– */
@media screen and (min-width : 415px) and (max-width : 500px) {
/* Styles */
}

/* Smartphones (portrait) ———– */
@media screen and (max-width : 414px) {
/* Styles */
}

You can then perform a Mobile Friendly Test at: https://www.google.com/webmasters/tools/mobile-friendly/