Earlier to book the VAC appointment we used to use this portal link: https://portal.ustraveldocs.com/
The updated procedure now involves registering as a new user. The specific steps for this process can be found at https://ustraveldocs.com/
Step1: Head over to the site
Step 2: Select your country , it will automatically redirected into new tab
Step 3: Create/Register user
Once you succefully confirm your email you will be able to reschedule and manage your bookings
Thanks
Ashish