Not all at once!
Ich will not survive above a certain temperature. The recommended approach is to raise temp to 87F, not to exceed 2 degrees change every 12 hours. If the fish are generally healthy and/or water is already near that temperature a slower rate of change is less stressful to them, but you must balance that against the disease which as you know can be deadly.
Be sure you maintain this temperature at least two weeks after the last disappearance of white spot symptoms to ensure the parasites have been eradicated, and observe the same rate-of-change precaution when lowering temperature afterward. Also, gases are less soluble at elevated temperatures so it's generally recommended that you lower your water level slightly so as to allow your filter's outflow to splash, compensating for the lower oxygen solubility.
If your heater doesn't have an adjustable thermostat you will need one that does. I recommend the Whisper Stealth brand if you need to pick one up, but there are several on the market.
Salt is also used to treat ich, but unless I'm mistaken the fish you mentioned are not very salt tolerant, certainly not to the level required to kill the parasites, so heat is the method you will need to use. Get started immediately!