I need to change the wordpress installation domain

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Follow this if the new domain is added as an addon domain:

How to move a website to a different directory

Every website is linked to a certain htdocs directory on your account. But sometimes you need to move a website from one htdocs directory to another. This may be necessary if: You are moving to a different domain name (e.g. a free subdomain to a custom domain). You have recreated your domain name and it was assigned to a different directory. Fortunately, there is no need to rebuild your website from scratch. It’s not difficult to move your website from one directory to another. How to move a…

Then you’ll have to change the website URL and the home URL for your website to work under the new domain; here’s a guide to do that as well, which is also listed in the article I linked to:

Migrating WordPress – Advanced Administration Handbook | Developer.WordPress.org