You can create a self signed certificate within HiveManager (if you're interested in this and you can tell me which HiveManager platform you are using (see guide below to determine this), I can give more details on how to do this), or you can purchase a third party certificate from a certificate authority(CA) such as GoDaddy.
Using a self signed certificate is not as secure as a third party certificate from a CA, and self signed certificates will still present a warning to end users that the site is not verified as safe.
If you're using a third party certificate, you'll want to make sure the CA gives you the Cert file (the file that has the domain name), the Server Cert file, and the Key file. If these are given as separate files, you'd want to concatenate them in to one file to import it in to HiveManager.
This guide will walk you through how to determine which HiveManager you are using, for reference: https://thehivecommunity.aerohive.com/s/article/Which-HiveManager-Platform-am-I-using
