you can find DSSP at http://www.embl-heidelberg.de/dssp/ or could prefer use
Procheck from the CCP4 series (http://www.ccp4.ac.uk/) and run it on your
pdb file by the "procheck [pdbfile] [chain number] [resolution]" command.
You will obtain 10 postscript files in which you can find drawn in the 6th
one the secondary predicted structures that you can write in your helix and
sheets part in your pdb.
Hoping that it could help you