By new account do you mean Apple ID?You can create an alias that would be attached to your current iCloud email. You can’t change the name of your current email account. Create a new account with the name you want, unless the one you are currently using as purchases tied to it. If that is the case, you can create the alias or live with what you have.
I don’t have that allow sending from option in settingsHere's a MacRumors guide about how to create and manage Apple Mail email aliases. You can create up to 3 aliases and use them just as you would your primary Apple ID email address.
How to Use iCloud Email Address Aliases
Apple enables iCloud account holders to use email aliases, which allow you to send and receive emails without disclosing your true email address. ...www.macrumors.com
At this point to help you get this sorted, it will help to know what device you're trying to do this on and which OS version it's running.I don’t have that allow sending from option in settings
Yes. When you create a iCloud email account, you are actually creating an Apple ID. If you want to create a new Apple ID, you can do it from the iPhone but, you need to be signed out of iCloud in order to see the option to create a new Apple ID.By new account do you mean Apple ID?