Evaluating AdminUI
If you are using a demo license key, when you create a user we give you the ability to set a password for that user. We do this to simplify the creation of users while you are evaluating the product. However, we do not recommend this for production installations.
In production
When you are using a production key we do not give you the ability to set a password for the user on the Add User screen by default. Our recommendation is to use an email flow for the user to set their own password. You can enable this via a webhook as explained here.
However, if, in your situation, you do want to enable the ability for an administrator to set the password for a new user, you can turn on this feature with the AddUserPassword as documented here.