process chains

i ve done with initial steps in process chains,, but i got stucked up in the plan view of the process,, where, i need to drag & drop the info packages.. after droping the info packages,, the start process,, is not being connected with the infopackage .... after that what is that i should do till end..

when exactly the process chains are required..?

why variants are used in process chains?

ashwin