You have to add a line to the nsd.tcl file. here is a sample:
ns_section "ns/server/${server}/modules"
ns_param nssock ${bindir}/nssock.so
ns_param nslog ${bindir}/nslog.so
ns_param nsperm ${bindir}/nsperm.so
ns_param civupload ${bindir}/civupload.so
# Load the mydir module
ns_param mydir tcl