As you may know, Damavand has many faces that mountaineers can use. The easiest path to summit, however, is the southern face. In this side of the mountain there are three camps, one is near Polour known as the base camp, the other is the Bargah Sevom camp, and the last is Atour Summer Camp. there is also a mosque in Goosfand sara that can be used, especially if one needs a shelter from the cold. Among all the camps, the one belonging to Atour is nearest to mountain and the base camp that belongs to mountain federation of Iran is the furthest.
the mountain is more than 5000 m. and you need a guide to accompany you in your ascend. If you don't have mountaineering background, you will probably face difficulties. The ideal plan for ascend takes three days with one day specified to acclimatization. believe me, skipping this day is Not a good idea. If you come through a travel agency, it would ease your travel to Iran since they provide services like Visa, Transfer, and guide.
The Average ascend from Atour Camp and Bargah Sevom to Summit is about 6-7 hours, and the descend will be probably around 5 hours so it will take a full day to ascend and come back and you will be really tired so its better to spend the night in the camp. You can contact me if you have more questions.