How should i approach limiting the amount of internet time my son has?

DO IT !!!: The nature of the question suggests that you have thought about internets for a while, but are delaying the implementation. Explain the limits, the reasons why there are limits, and the consequences of breaking those limits to your child. Place all all internet accessible devices where they are easily monitered. Set a start date and do it ! once started, do not relent.

Offer choices: The aap and other groups encourage parents to limit a kids combined "entertainment" television/computer/mobile device use to a total of 2 hours /day. School work is excluded from this total. There are ample ways to lock these sources if a kid is not complying with the limits you decide to set.