Waterside pavilion: a pavilion built on or near water.
Appropriate time: Appropriate time, just like "auspicious day and good time".
Zhi: ascend, ascend.
Xiang Wan: At dusk.
The waterside pavilion should be facing away from time to time, and the mountain tower should look towards the evening.
On an auspicious day, go to the waterside pavilions and watch the mountain pavilions when the sun sets.