Import the PFX Certificate. This is easy; just double click on the PFX file and this will launch the Certificate Import Wizard. Follow the instructions.
Update the post build events in order to use signtool. In my case, I launch a small batch file which iterates over the specified files, signing them:
for %%f in (%1) do signtool.exe sign /a /n "OPaC" /d "OPaC bright ideas" /t http://timestamp.verisign.com/scripts/timstamp.dll "%%f" I am specifiying which certificate to use with the /n option and the /d option is necessary to make the Vista installer happy. Without it, the MSI file which appears in the UAC prompt will have a random name.