Each Droplet is only allowed a single IPv4 IP, so you would not (currently) be able to configure your Droplet to support multiple IP addresses. Instead, you would utilize the primary IP as the main IP for multiple domains.
All modern web servers (Apache, NGINX, Caddy etc) provide support for what is called SNI, or Server Name Indication, which allows a single IP to support not only multiple domains, but also multiple SSL certificates (if SSL is a concern).
SNI does not require any further configuration and it’s native to all three of the web servers I listed above, so you wouldn’t need to specifically configure anything differently to utilize it.
If you physically require each website to have a unique IP address, you would need to deploy each website to its own Droplet.