There are lots of information in this forum on rs232 comunication. Perform a search for rs232. I once posted a question on this subject (check link).
Before you get started, check TDS3014 manual for correct port settings and cable configuration.
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=506500000008000000AE2F0000&UCATEGORY_0=_49_%24_6_&UCATEGORY_S=0