Скачать или смотреть Android Custom Ringtone Tutorial (Custom Notification)

Setting custom ringtones & notifications sounds is really simple on Android and you don't even need any special apps to do it.
-Connect to your computer
-Find the "Ringtones" folder or "Notifications" folder under internal storage (not the SD card)
-Drag a file from your computer to the phone
-Navigate in your Android settings to whereever you change the Ringtone
-(It's in different places on different phones, but google it if it's not obvious)

-Use Audacity or another sound editor to trim songs/audio shorter
-Good length for Ringtones is 30 seconds
-Notifications shouldn't be more than 3 seconds

Audacity http://www.audacityteam.org/download/
Exporting MP3 with Audacity    • How to Save MP3's in Audacity With the LAM...  
AirDriod, the screen mirror app I used https://www.airdroid.com/