Welcome to the Pentax Forums!
Your Spotmatic is very generic in regards to flash support. It was made before the days of dedicated flash. The PC connector on the camera is standard and any modern speedlight that supports a PC cable can be used. If your flash or triggers require a hot shoe (no socket for cabled sync), there are adapters that fit between the flash foot and a cold shoe. There are no voltage requirements or restrictions. Any electronic flash capable of manual operation will work as will most bulb-type flash guns. Use the X terminal for all but (very rare now) FP type flash bulbs.
I am assuming that your Spotmatic has no flash shoe. If that is the case, you will also need a mount for the flash. Pentax sold an accessory shoe that slips on over the viewfinder eyepiece. I have used them and they don't work very well and tend to slip off the camera. I would suggest a flash bracket of the type that attaches via the tripod socket Many of these also have a handle. That is what I currently use.
http://www.bhphotovideo.com/c/buy/Flash-Brackets/ci/653/N/4168864826
Steve