Your inter/national organization likely uses a different system to add new members if you do not have the "Add Members in Mass" or "Add Member" buttons as reflected in the below screenshot of Vault > Chapter menu > Add New Members.
If you only see the option for ""New Member Form," as reflected below, your inter/national organization adds new members in another system, and those member records will then filter into Vault.
If you are unsure what your organization uses to add New Members, please reach out to your Inter/National headquarters in inquire for more information.