First of all, make sure that the tones you want to add to your device are available in the computer. There are many ways to get ringtones. You can either buy a CD, or download them from internet. The cellular companies also offer different ringtones these days.
Connect the EVO to your computer through USB cord, which comes with the device. Choose the connection type as ‘Disk Drive’. Go to ‘My Computer’ and open your SD card, where you will find a folder named as ‘Notifications’. If there is no folder of such kind, create one by yourself by using the right-click menu.
Copy ringtones from your computer, and paste them in the folder. Once the copying is completed, you can change the connection type to ‘Charge Only’. You can now disconnect your device from the computer.
The new rings will be shown in the directory. Go to the ‘Sound Settings’ in your phone, and set the ringtones, which you have just transferred. You can set any tone as your notification sound. Go to your SD, and play the sound. Push the menu button, and select the option to add as a ringtone.
You can also get tones either by using downloading or Bluetooth. But for this, you need a file manager to move files from ‘Downloads’ to ‘Notifications’ folder.
Apps such as ‘Android Assistant’, ES File Explorer, and Astro File Manager’ can help you in this regard. Use Play Store to download these applications.