Vantage Menu Font

Hello I am currently using the vantage theme and was wanting to use some custom CSS to change the menu font however I must be doing something wrong because anytime I try and change the menu font it doesn’t seem to want to change.

Can anyone suggest what im doing wrong here?

Thanks

/* Vantage set menu font family and weight */

.main-navigation a {
font-family: ‘Rochester’, cursive;
font-size: 16px;
}
}