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/
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AirDriod, the screen mirror app I used https://www.airdroid.com/
On this page of the site you can watch the video online Android Custom Ringtone Tutorial (Custom Notification) with a duration of hours minute second in good quality, which was uploaded by the user TanUv90 03 October 2016, share the link with friends and acquaintances, this video has already been watched 2,707 times on youtube and it was liked by 11 viewers. Enjoy your viewing!