Hi@akhtar,
To connect any Cloud, Terraform has a keyword named provider. You need to use this keyword to connect your OpenStack Cloud. You can use the below-given code.
provider "openstack" {
  user_name   = "demo"
  tenant_name = "demo"
  password    = "647a07963bf74375"
  auth_url    = "openstack_url"
  region      = "RegionOne"
}
Copy this code in a file with .tf extension and run the below-given command.
$ terraform init
$ terraform apply -auto-approve
I hope this will give you some ideas.