Can I use 1 email address for multiple accounts

No, an email address can only be associated with a single AppleID. You can use one AppleID on many devices though - just sign in during setup with the AppleID you already have to use that same AppleID on another device.

Using 1 email address for multiple accounts-do you mean 1 email address for multiple apple ids? Please clarify.

Trying to set up additional phone? You may use the same Apple ID (email) that you already have if you have one or create a new Apple ID which will require a different email address.

https://support.apple.com/en-us/HT204316