i want to connect my aws Neptune instance using bolt how to get credentials for it .

Here are the docs on how to connect to Neptune using Bolt in Python against a Neptune cluster that is configured to use IAM Authentication: https://docs.aws.amazon.com/neptune/latest/userguide/access-graph-opencypher-bolt.html#access-graph-opencypher-bolt-python-iam-auth.

You'll need IAM credentials that provide access to Neptune's data plane: https://docs.aws.amazon.com/neptune/latest/userguide/iam-data-access-policies.html

Ensure that you are connecting to Neptune from inside the same VPC where Neptune is hosted, as Neptune is not accessible outside of it's hosting VPC.