what is the procedure of visiting great wall of china from gangtok {Sikkim,India}?

First, you should apply for a visa to enter China. Second, you may fly from India to Beijing. Have you decided which section to visit, Badaling, Mutianyu, Simatai or Jinshanling? Anyway, you need to take buses from Beijing to visit the wall. If you can tell which section you want to visit, then I may help you figure out how to go there from Beijing.

u can get L visa type t visit , then it's about which city u wanna go, it's in beijing, shanghai ,qinghuandao, chongqing, so if u wanna visit in beijing Then you need to take subway line 4from beijing south railway station to reach Xizhimen Station. It takes around 30 minutes. Getting out of the Exit A of Xizhimen Station, you walk to Beijing North Railway Station to take S2 train to reach Badaling. It takes 1 hour and 20 minutes. or u can go by bus