I'm unable to createa jira here.
When I try to submit the issue I get the below error.
Assignee: The default assignee does NOT have ASSIGNABLE permission OR Unassigned issues are turned off.
I've attached the screenshot as well.
Also, I couldn't find any field with name as assignee. How can I be able to submit this JIRA successfully.
Assingnee is a build-in field. Go to project admin console/users. Find where to set project lead and default assignee. This is a default assignee to assign new created issues. To find assignable permission go to permission scheme assotiated to this project. Find assignable permission. Now yoy can to solve your trouble.
You may be able to reveal the "Assignee" field in this screen by ticking the appropriate box in the "Configure Fields" settings, which you can access using the button in the top right of the dialog. This setting should (I beleive) persist, so once you've done it, it should appear whenever you create an issue.
Vasiliy's answer may also be worth applying if you want to set up a default assignee without needing to select them when creating the issue.
What solved it in my own case:
Jira defaults newly created issues to the project lead of that particular project.
The project lead exited the company. With his access revoked, Jira wouldn't create issues and default the assignee to a suspended user. Hence you have to change this.
To change the project lead and default assignee, go to Project Settings and navigate to the Details tab to change the default assignee or project lead
