how to upgarde oppp A37 android 5.0 to 6.0?

i ve an oppo A37 how to upgrade 5.2 to 6.0 or 7.0 compney not offering upgrade then how to upgrade?

from Android Forums at AndroidCentral.com - Ask a Question //forums.androidcentral.com/showthread.php?t=773725&goto=newpost
via IFTTT