Make sure he drains the tank and the engine. Put two quarts in the tank, crank the bike and let it idle to 5 minutes or so (don't rev it up, that causes the oil to froth). Shut it off, the dip stick will read little or no oil, add the other two quarts, being careful on the second not to overfill.
The tank is kinda pyramid shaped on the top, making it easy to over fill.
Make sure to use new washers on the drain bolts. The Yamahas are true crush washers and cannot be reused. If you substitute aluminium or copper washers you can use them a couple times before repalcing.
I'm sorry... the highlighted area is WRONG. Here is the NOTE in the service manual. It is pretty much very correct:
• Pour the engine oil in several stages.
• First, pour in 2.5 L (2.2 Imp qt, 2.6 US qt) of oil, and then start the engine and rev it 3 to 5 times. Stop the engine, and then pour in the remainder of the specified amount.