They show you fourteen words, one at a time, and you type in the first three words that come to your mind in the three empty fields below the prompt-word.
If nothing comes to your mind, you're supposed to type "no response." I had one word where that happened (the word was "grief", and instead of seeing an image I could describe, or a color, or hearing the word echo and mutate into various sound-alikes, I actually felt an attenuated version of grief itself), so I entered that into all three fields.
They do want everyone taking the test to be a fluent English speaker, but other than that there are no restrictions. And you can be from anywhere, and you don't have to be a native speaker --- just fluent.
Probably, if your English is good enough for you to be reading this blog, you can participate in this study.
