i need to create one workflow which receive request from web-hook & request containing JSON payload ( around 6 fields ) and data should append in sheets.
i am completely newbie in n8n.
Hi @ironman_Cloud, welcome to the community 
The exact design of your workflow will depend on how your webhook payload looks like.
Let’s assume you are POSTing a payload like below:
{
"Name": "Foo",
"Message": "Bar"
}
This will arrive on n8n’s Webhook node like so:
Now as you can see the data arrives in the body field. For n8n to be able to append data to a Google Sheet, you’d need to make sure the fields in n8n match the columns in your Google Sheet.
So, let’s assume your Google Sheet looks like so:
In n8n you can use the Set node to define a new item structure which could work like so:
At this stage we have the required data structure and can continue with the Google Sheets node:
This is the result:
And here’s the workflow in its full glory:
Hope this helps! Let me know if you have any questions on this.