Hey Elena,
Hopefully this isn't too late/helps someone else:
<style>
h1{
font-family: roboto!important;
}
h2{
font-family: roboto!important;
}
h3{
font-family: roboto!important;
}
p{
font-family: roboto!important;
}
</style>
This works. You can change Roboto for any font of your choice.