(Optional) if your Jira is hosted on AWS EC2, you can manage Lambda permissions through Roles. i.e. Identify your EC2 role and add permissions (i.e. LambdaFullAccess).
On AWS, Create IAM user with Lambda Permissions i.e. go to Identity & Access Management (IAM) → Users → Click Add User
Username: e.g. scmenthusiast
Access Type: Programmatic access
Set permissions: Click Attach existing policies directly → Choose Policy (LambdaFullAccess)
Click Create user.
That's it, take the note of Access Key ID & Secret Access keys.
On Jira, Go to Manage apps → Amazon IAM Users Access Keys → Add New IAM User.
Option if you don't like to manage IAM access keys in Jira database
In Jira, Create IAM User without Access key ID and Secret access key.
Go to your Jira host, copy Access key ID and Secret access key to ~/.aws/credentials file.
$ vi ~/.aws/credentials
aws_access_key_id = ASIAYQXMDDN5CGUE****
aws_secret_access_key = qtQlqQONtbU2H6MNb2VJfqRpOALlVto8*****