How to Create Access Token in Magento 2 Integration

You have to pass url like,

http://clients_magento_shop/rest/V1/integration/admin/token

Pass body method like this,

Post Method:

Body:
{
    "username":"admin",
    "password":"admin123"
}

You cannot find the token and token secret from Magento backend. You need to query these from the database directly.

First login to Magento backend and go to System->Web Services->REST - Oauth Consumers. Take a note of the oauth consumer you need the keys for. You can also find consumer_key and consumer_secret from there if you click on that consumer's row. However it's easy to find the keys from DB also:

The consumers and secrets are stored in DB table oauth_consumer. Find the necessary user by column "name" from there and copy the columns "key" and "secret". These are "consumer_key" and "consumer_secret". Take a note of entity_id in oauth_consumer table.

Then look at DB table oauth_token. Find a record by consumer_id and copy columns "token" and "secret".

Now you have all the 4 keys that are necessary to make a fully authenticated Oauth request towards this Magento instance.

Reference: This is a duplicate - Rest api, tokens?