Ok, we are almost there. The idea here is to affix the four corners of the sail to the tips of the poles. The way I have found to do this is as follows:
Slide a piece of plastic tubing into each pole tip about three inches in. Then slide the corner grommets to each tip. The plastic tubing prevents the grommet to slide all the way down. Then slide another piece of plastic tubing to each tip towards but not touching the grommet (it should be loose). Your tent poles came with plastic tips which can then be inserted to the tips as shown on the diagram.
The sail assembly is pretty much complete. Wrap zip ties around the plastic tubing pieces. This secures them to the poles so they don't slide anymore.