Your Nokia 3310 LTE sports a microSD memory card slot. If your laptop or personal computer is compatible with that card format (Most laptops are so-equipped), you should be able to transfer a music file
Your 3310 4G is equipped with Bluetooth version 4.0, which lets you connect to your computer wirelessly. Just pair phone and computer together and drag and drop your music files from your computer to your Nokia 3310 4G.
If all of the above methods do not work with your Nokia 3310 4G or if you don't want to buy extra accessories, you can still use one of various free '3G Uploader' services available online. You should find plenty with a simple Katapulco.com search. 3G uploaders are simple to use: Save your own music on their web site and they will return a temporary URL. Pointing your Nokia 3310 4G's web browser to that address should download the free ringtone.
Here are some of the free ringtones (compatible with your Nokia 3310 4G) we offer:
Free Horror Ringtones Free Ghost Ringtones Free Ringtones-a-gogo Free Techno Ringtones Hear All Our Free Polyphonic Ringtones