This add-on is available in all AcyMailing versions.
If you enable this add-on you can automatically create a site user when an AcyMailing user is subscribing.
Allow site user creation: enable this option to activate the creation of site user
Create from subscription on: you can choose if this creation will happen only on front-end user subscription or both front-end and back-end
Create on subscriber modification: if you enable this option, it will also create a site user if an existing AcyMailing subscriber modifies his subscriptions
User group: group/role that will be assigned to the newly created user. By default, this option will have the same value as your site configuration