If you completed all of the steps described on the installation page (https://ww.wp.xz.cn/plugins/wordpress-mu-domain-mapping/installation/), then you can do the following to complete the mapping of domains.
1. Under WP network admin, go to sites. Hover over your site and in the lower left of your browser, you should see a url pop up. At the end of that url is an ID number. You’ll need this for the next step.
2. Go to Settings/Domains.
3. Enter the ID number in the site ID field.
4. Enter the url that you are looking to map in the domain field. You’ll need to decide whether you want to include “www” or not in the primary domain for that site. Leave off “http://”.
5. Click the save button.
6. Add another entry with the same url, but this time with/without the “www” (depending on what you entered the first time). So, if in step 4 above, you entered http://www.myurl.com, in this step you should enter just myurl.com. This will then direct myurl.com to the http://www.myurl.com version.
7. Uncheck the “primary” box.
8. Click save.
The above steps worked for me,…hopefully it works for you too! Good luck.
which asks for site IP which I have added however there is no effect.
The IP address field is for display on the user mapping tool. It does not affect how the plugin functions.
Do I have to do anything (change cname or a record) on the actual domains
Yes, you need to change the DNS of the domain(s) you want to map to point to your WP install. You can use either a CNAME or the Ip address in the A record.