There are no hard rules for installing this rack, but below you can find how I do it.
Summary
1. Install top platform. This is the long hoop section with the small stainless clamps attached to it. It connects to the bike with the seat post clamp (or, optional Bridge Adapter), and can be mounted with the bend pointed upward or downward, depending on whether the clamp is above or below the level of the rack platform. I like to install the top platform so that it will be about 1.5” / 4cm above the top of the tire at its closest point.
2. Install the lower struts to the stainless clamps. The lower struts are installed with the mounting tabs pointed toward the rear of the bike. The stainless clamps mount so that they sandwich the tabs on the lower struts. Slide the connection clamps along the top platform and angle the lower struts until the seat stay mounting blocks touch your bike seat stays. The rack is strongest when the connection between the top platform and lower struts is close to the back. The connection clamps should be no more than 6” / 15cm from the back of the rack.
3. Install the seat stay mounting blocks. Wrap the seat stay with layers of protective tape at the point where you will install the mounting blocks. I used to use thick butyl tape for this, but have since found that it melts in the sun and makes a big mess. So, now I recommend just using several wraps of vinyl or silicone electrical tape. Then, use pliers to tighten the heavy duty cable ties through the mounting blocks. You want these as tight as you can get them without damaging them. If there are cables/hoses running down your seat stays, the tape and cable ties should run underneath to avoid crushing them.
4. Tighten all bolts. Once everything is in place, tighten all the bolts firmly so that nothing can slip.