Once you created your xml file, you will need to save it as RingList.xml.  Then tftp your RingList.xml and any of the ring tones to your routers flash.  Once you have finished, you will need to use the tftp-server command to be able to access the files.  For example:

IP-PBX#config t
Enter configuration commands, one per line.  End with CNTL/Z.
IP-PBX(config)#tftp-server flash:RingList.xml
IP-PBX(config)#tftp-server flash:horn.raw