Sorry for the confusion. There's no need to install WordPress on your local computer. I actually meant if you tried changing the nameservers using a computer instead of an iPad.
To point the domain you registered at WordPress.com to another server (hosting service), please follow the instructions here:
Note you will need to obtain the name server values from your current host. You should be able to find them on their support documentation, or contact them and ask for the information. (Name servers may be referred as "nameservers" or "NS records" instead.)
Hope this helps - let us know if you have any more questions!