Kindly suggest procedure of SEO And How to create multi domain on single website ?

Please follow the below link to set up SEO:
https://help.storehippo.com/topic/seo

For setting up multiple domains you can add a new domain same as you have added your primary domain from your domain provider.
Please follow the below links to set up the domain:
https://help.storehippo.com/topic/domains

https://help.storehippo.com/topic/setting-up-domain