Move wordpress site from main domain to add on domain

Hi.

I have a hosting package for https://www.site1.com. I use add on domains to host other domains including https://www.site2.com. I now need to move my wordpress site from site1 to site2 but I don’t want to lose my search engine rankings and results. Can anyone give me or point me to an idiots guide to doing this. I have found guides online but they all refer to transferring from one host to another whereas mine is just one host but moving from the main domain to the add on domain.

Thanks