To change the default Magento URL/path which is www.domain.com/admin to anything please follow these steps:

You need FTP(File Transfer Protocol) access or File Manager if using cPanel.
Step 1: Open file app/etc/local.xml, search for:

<admin>
        <routers>
            <adminhtml>
                <args>
                    <frontName><![CDATA[admin]]></frontName>
                </args>
            </adminhtml>
        </routers>
    </admin>

Just change the admin to whatever you wan to replace default admin.

Step 2: If you are already logged in: go to System >> Cache management >> Refresh all
If you aren’t, then you can refresh the cache using SSH command line

You need to be in root directory of magento do perform below command.

rm -rf var/cache/*

All done, now you can use new admin URL/path instead of old.