As per the instructions I haved done the follwoing
1) Assigned a Dedicated ip (188.8.131.52) to the main multisite website webkuteer.biz
2 ) created a subdomain http://naveen99.webkuteer.biz
3) registered a domain http://www.naveen99.com (the nameservers of this domain are same as webkuteer.biz)
I tried to login to the admin dashboard of http://naveen99.webkuteer.biz and from the Tools menu I opened Domain Mapping and entered the domain "www.naveen99.com"
I am getting the the message (screenshot attached)
Domain name is unavailable to access
We can’t access your new domain. Mapping a new domains can take as little as 15 minutes to resolve but in some cases can take up to 72 hours, so please wait if you just bought it. If it is an existing domain and has already been fully propagated, check your DNS records are configured correctly.
I have provided support access in wpmudev for you to access my site and check if any issues are there