How to replace a custom platform's homepage with another homepage from another platform domain?

[sihanedutech]

I have a question regarding 301 permanent redirection. I currently have three websites, each hosted by different platform/CMS: one by Wix, another by WordPress, and a custom built CMS. I want to have all my three websites to be under the the custom build CMS's URL. What I am most concerned about is that I would like to have the home page of my Wix website to become my custom build CMS's new home page and the original content currently under my custom build CMS would be updated under new sub directories (in which I have access to the custom build CMS's source code). I have never done a 301 redirect before and I would like to know if there is any additional thing I need to do to my current custom build CMS besides assigning all my current content under my custom build CMS to new directories before executing 301 redirects?

[victor.celer]

If you haven't done 301 redirects before you can start reading the dos and donts.

For example, many websites use 301 redirects to force "www" and/or "https". Crossdomain redirects are mainly used for migration.