Hello Katherine, 

You can try changing the font by adding this custom HTML to the page where you have your Amelia shortcode:

<style>
.amelia-app-booking input[type="text"], .am-modal.am-in-body input[type="text"], .amelia-app-booking input[type="email"], .am-modal.am-in-body input[type="email"], .amelia-app-booking input[type="tel"], .am-modal.am-in-body input[type="tel"], .amelia-app-booking input[type="url"], .am-modal.am-in-body input[type="url"], .amelia-app-booking textarea, .am-modal.am-in-body textarea, .amelia-app-booking select, .am-modal.am-in-body select, .amelia-app-booking .form-control, .am-modal.am-in-body .form-control, .amelia-app-booking .am-stripe-card, .am-modal.am-in-body .am-stripe-card,
.amelia-app-booking h1, .am-modal.am-in-body h1, .amelia-app-booking h2, .am-modal.am-in-body h2, .amelia-app-booking h3, .am-modal.am-in-body h3, .amelia-app-booking h4, .am-modal.am-in-body h4, .amelia-app-booking p, .am-modal.am-in-body p, .amelia-app-booking span, .am-modal.am-in-body span, .amelia-app-booking div, .am-modal.am-in-body div, .amelia-app-booking section, .am-modal.am-in-body section, .amelia-app-booking ul, .am-modal.am-in-body ul, .amelia-app-booking li, .am-modal.am-in-body li, .amelia-app-booking a, .am-modal.am-in-body a {font-family:fantasy !important; font-size: 15px !important;}
</style>

We put font fantasy and size 15px as an example, but you will set the font and size you want there. 

Hope this helps!

The available time slots for the appointments are determined by the employees' work hours. So, you need to setup employees' work hours as you want not the company work hours in Amelia -> Settings. 

Let me know if this helped!