I added a column to a table which is being replicated. Will that column be reflected at the target? If not, how can I achieve this??

No. If you saved the scripts used to create the replication, then you can see where each column is defined separately. If you did not save the scripts, you could generate a new replication scenario on a test machine and look at the scripts before they are submitted by the GUI interface. You will also need to add the column to the target table.

it can be done manually - if you know the tables and their layout
it should be added to the capture tables - the cd tables should be changed..
it should be added to asn.ibmsnap_subscols...
Use the gui of replication center if not familiar with manual procedure

That is what I said. It is not done automatically.

What I suggested was to create a new replication scenario (if the old scripts were not saved), and look at what the GUI does (Show SQL) to figure out what needs to be done manually fo each column. Or one can delete the old definitions and start over.