You can sign up for your own developer org enabled with OmniStudio by clicking here.
After clicking, you will be directed to the page where you can fill in all the details and sign up.
After signing up, a message will be sent to your email. Fill in the details, verify the message, and create your password.
Note- Please wait after 20 minutes for email verification.
Click verify Account and create Password
Password = Use Alphabet & Number And special character.
Example=Abhi@123
I hope you understand how to create a new org in Omniscript for Salesforce.