I purchase the kits from Western Branch Diesel. They are located in Manassas, Virginia. The kit comes with a sample bottle, label, and instructions.

First warm the engine oil to running temp.
Let the engine oil cool enough so that it will not burn you when draining.
Drain engine oil for a brief second and then capture enough oil to fill the bottle.
Fill out the label completely; noting it is a gas engine for an ATV.
Set up an account on the 1 800 number.
Send off the sample.
In a few weeks you will receive the analysis in the mail.

You may be able to purchase a sample kit from NAPA or another part store. One could also look online for such services as well.