Rinsing the bottle with pool water from 18-24 inches below the surface, then filling it from the same depth will yield best results possible. Be sure to keep the bottle shielded from the sun and not heated above room temperature. Take the sample immediately before departing straight to the testing location. Lastly, if the pool store is more than 15 minutes from your house, the already unreliable pool store testing becomes even less reliable for FC.
Congrats on your new test kit! I'm guessing you ordered the k2006 which is now sold and shipped by Amazon now! If so, please post the soonest expiration date of the chemicals you get because if it is fresh enough I have a friend that needs to order one too. Thank you!