Did I lock up the engine?

The engine is not turning over. However the starter is making a loud clicking noise?

Is the engine turning over? If not have your battery tested? If battery is good, I would pull the spark plugs to see if it turns over then and also spits out anti-freeze from the holes left from where the spark plugs were after you removed them and left them out to test, if so its a head gasket failure. Note which side does or which plug holes does so if its a v-6 so you know which is bad, I fit does need head gaskets I would still replace both sides and have the heads inspected by a head machine shop before re-using.

I would still test battery and charging system to be sure if its not working correctly, Know that I would also pull those spark plugs before continuing to try to start it as if its hydro-locked, cranking it over can and will pull a rod loose from the piston, and instead of a head gasket its a rebuild if that happens, better safe than sorry, not saying its a head gasket 100%, I am trying to inform you it could be and how not to ruin your engine, So stop trying to crank it up until you pull the spark plugs and leave them out when cranking to see it it turns over, it may have fluid on top of piston, this (if so) needs to be let out before trying to start it up. It will not crank up (run) with the spark plug out. It will let out any fluid if any. If battery is dead, then replace or charge it up if that is the case then it likely the cause and may not need to pull spark plugs.

Of course you will need a new cap to stop this from happing again, but get it running or see if its a head gasket issue now and if you want to fix it. Either way you may need to replace thermostat and/water-pump, hoses,, make sure fan(s) are working. if its going to be kept on the road.