I'm trying to do the tourist flight contracts in KSP, but can't figure out where I can find the tourist kerbals to add them to my vessel?
When you accept a tourist contract in the mission control building, the tourists are added to your astronaut roster. You can then put them into command pods just like your real astronauts: With the crew tab in the VAB/SPH or from the dialog which appears when you click directly on the runway/launchpad.
Keep in mind that a command pod which is only manned by tourists does not count as having crew, so you need to keep at least one seat for a real astronaut or add a probe core. Also, tourists can not go on EVA.