Authorize an org using sfdx authorize dev hub

Step 1: Create a project.

Step 2: Press Ctrl+Shift+P, Enter "SFDX: Authorize a Dev Hub" as shown below. This will take us to login page.

STEP 3:  Enter the login id and password.

Step 4: Go back to Visual Code Studio where we can see the status of authorization as shown below.

Step 5: To create a scratch org we need to enable a dev hub as shown in the below images.

Step 6: These are the two new objects which are created after we enabled dev hub in our org as shown below.