If you are using the waveform functions you can add them together using the add waveforms function find under:
Functions -> Waveforms -> Waveform operations
Generating the waveforms and analyzing them can be done using the different waveform functions on the Analyze palette.
If you in LabVIEW go Help -> Find Examples -> Search...and search for waveforms you will find a bunch of nice examples (not absolutely sure what is included in the evaluation package though...searching here on the zone is an alternative..).