Dear Satish,

I hope it is not too late to answer this post.

The wind load produces a horizontal force acting at the CG of each element (shell/head/cone etc). This load is used to compute the moment on top of the legs. So, you will have contributions from wind load on each of the elements which will be totaled to get a final wind moment on top of the legs.

The legs are then designed using this moment and weight of the vessel.