According to website Passengers must register themselves before reaching Bharmour and have a printout. You can call on given number in website for more information. hpchamba.nic.in/manimahesh-yatra/
According to website Officially,This journey will be from 26-08-2024 to 11-09-2024 and Registration is mandatory. There will be no registration after 11 September. So I think you should contact authority or a travel agency of Chamba for more information.