-THIS IS FOR CPUS THAT HAVE A HEAT SPREADER ONLY. A BARE DIE WILL INSTANTLY FRY WITH NO COOLER ON IT. If it's a bare die, put the cooler on it and run something like prime-95 or with a gpu furmark for about 10 mins. Turn it off, take out the cooler, the paste should be melted. (That pink AMD goo would not come off unless you did this) Well the days of the athlonxp are gone so this is rare today.
There is a much easier way. Turn the computer on without the cpu cooler. Leave the cpu cooler fan plugged in so there is not a error.
Just keep your finger on the cpu and when it's too hot to the touch turn the computer off.
Just use toilette paper or Kleenex or just a soft cloth or rag and rub the now melted paste off.