In order to define a new REST Connection, follow the steps below:
1- Click 
while on REST Connections tab. You can select Folder to create a folder to organize your REST Connections. To create a REST Connection, select Connection.
2- This will open up the REST Connections tab
3- Specify a name (60 characters max), URL, and comments for your REST Connections.
4- Select the method for the connection from REST Options. GET method does not support body, but POST, PUT, PATCH and DELETE can be used with a body (payload).
6-The payload is optional and can be added as Plain Text or as Multipart where a multiple body parts can be added with custom field names.
7- Click Test Connection tab and click Test Connection to test and show the response.
8- If your request requires authentication and you see status code 401, select the Type under Authentication Options and enter the Username and Password.
9- If the selected method is POST or PUT, you can upload attachments by clicking Multipart option below.
10- If your REST endpoint requires authentication, you can use the Authentication Options to add your information. Supported authentication methods:
A. Basic
B. Digest
C. NTLM
D. By headers that can be added above the Payload
11- Hit Save or Save & Close to save your REST Connection.
12- You can now use the REST connection in your test case with REST commands.