add-user-iam.bat or add-user-iam.sh allows to create admin user from command prompt. The following example shows how to run this command to create a new user called "newadmin" by providing a password of your choice
C:\Program Files\CA\DevTest\IdentityAccessManager\bin>add-user-iam.bat -u newadmin
Press ctrl-d (Unix) or ctrl-z (Windows) to exit
Added 'newadmin' to 'C:\PROGRA~1\CA\DevTest\IDENTI~1\standalone\configuration\keycloak-add-user.json', restart server to load user
Press any key to continue . . .
Restart IAM Server and now you would be able to login to IAM as 'newadmin'. Once you login to IAM as newadmin, you would be able to reset the password of default 'admin' user