Take any EMU going towards HWH[lots of them go, usually they come from KGP side], many long distance trains also stop here, they can also be taken. Sealdah lies on a different route and direct connectivity via rail isn't possible. One option is to take a train to HWH and board a direct bus for SDAH[There could be smaller road routes going from SRC to SDAH but I am not aware of that].