Your Round Pavilion can be set up either with or without the custom fitted ground cloth. If you're setting it up with the cloth, be sure the ring is centered on the ground cloth when you're measuring out the intervals for the guy rope stakes, using the guide knots on the ropes as an index. Also be sure that the flat sides of the ring are parallel with the flat sides of the ground cloth. You can then use the ground cloth's corners to locate the sidewall stakes.
If your tent was not supplied with the ground cloth, locating the sidewall stakes can be a little trickier. Remember that the tent walls flare out one foot beyond vertical (for the 16' round, the walls flare out two feet from vertical. But there's an easy way to locate these stakes so you end up with a nice round footprint instead of an oval one.
On your wind prop, make a mark three feet from one end (for 16 round tents, the mark should be at two feet). Once the tent is standing on the center pole, make sure that the center pole is vertical and that all the guy ropes have approximately the same adjustment and tension, ensuring that the center pole is centered within the guy rope stakes. Now set the end of your wind prop against the stake and lay the prop down so that it's pointed at the center pole. The mark on your wind prop indicates where the sidewall stake goes.
With this method, you can accurately locate the six stakes that are closest to the rope stakes. Stake down the sidewalls at these locations. To locate the rest of the stakes, go to the vertical seam between each of the stakes you just installed and grab the stake loop at the bottom of the seam. Pull outward on the stake loop as far as it can go, and drive the stake through the loop.
If you have a 16' round tent, you have still more stake loops, in between each of the vertical seams. For most conditions, you won't need these at all. If it's really windy or you want to increase the seal between the sidewall and the ground, you can use these stakes, but you don't need to pull outward on them.