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How can I move my erpnext site to a custom app

Hi there,
I have a website built, and now I need to export that website to a custom app, and wehn install this custom app into a new erpnext to have my website running into this new erpnext.
I tryed to copy all the content from the erpnext “sites” folder into my app’s www folder. I installed the app into a new erpnext vm, but the website is still the default one.

Can someone help me pls… any advice?
Thank you all in advance.