Your Tempo is equipped with a microSD memory card slot. If your laptop or personal computer has a slot for that kind of card (Most laptop computers are so-equipped), you should be able to transfer music files
The ZTE Tempo is an Android smartphone and the Android market offers a bunch of free ringtone apps such as MP3 Ringtone Maker, Myxer and more.
Since your Tempo has a sound recorder (also known as 'voice memo'), a very straightforward technique involves just putting your phone by your computer's speakers, playing whatever song, music or sound you'd like as a ringtone, and recording it -- you can even use your voice, your child's voice or even your cat's 'meow!' Record it with your phone and 'voilà!' Unless that function was specifically blocked on the ZTE Tempo, you should be able to navigate to the ringtones sub-menu and assign that recording as a ringtone. Of course, the sound quality won't be perfect but, at least, it's free!
Learn more about making your own free ringtones
Here is a sample of the all free ringtones (compatible with your ZTE Tempo) we offer:
Free 'Unclassified' Ringtones Free Ghost Ringtones Free Short Ringtones Free Techno Ringtones Hear All Our Free Polyphonic Ringtones