1. The user should have an account on https://www.linkedin.com
2. Create a company page on Linkedin
3. Visit https://developer.linkedin.com/ & create an app
4. Use your Page name during app creation.
5. Add Product Share on LinkedIn & Sign In with LinkedIn using OpenID Connect under Product Tab
6. Go to Settings and verify LinkedIn page
7. Go to Auth tab and on the right side you have OAuth 2.0 tools to generate an access token
8. Once you get access token use Postman to get User Asset ID

See on Youtube https://youtu.be/3JqpUyKukyw

Linkedin API Details:

Get User Information :

Method – Get & URL: https://api.linkedin.com/v2/userinfo

Create a TEXT Post

Method – Post & URL : https://api.linkedin.com/v2/ugcPosts

Request Body:

{
    "author": "urn:li:person:<userInfo>",
    "lifecycleState": "PUBLISHED",
    "specificContent": {
        "com.linkedin.ugc.ShareContent": {
            "shareCommentary": {
                "text": "Hello World! This is my first Share on LinkedIn!1"
            },
            "shareMediaCategory": "NONE"
        }
    },
    "visibility": {
        "com.linkedin.ugc.MemberNetworkVisibility": "PUBLIC"
    }
}