From the railway station at Howrah you have to get to (Block AF of) Salt Lake. In case of confusion, some landmarks are Baisakhi which is a ten-minute walk from the Institute and Bhabha Centre (officially called Variable Energy Cyclotron Centre, VECC) which is a neighbouring institute.
You may take a pre-paid taxi from the counter if available, but avoid cars or even taxis unless they agree to go by the meter. There are two kinds of meters: old meters, with starting reading Rs. 5 and digital ones, starting with Rs. 10. In the former case, the correct fare is obtained by multiplication by 3.6 followed by addition of Rs. 2, while in the latter case, the multiplicative factor is 1.8. You can also try bus S-18 upto Baisakhi. Some minibuses (with `Salt Lake' written on the body) and buses 71 and 215A are also available, but these may get crowded at certain hours.