Parsecs are the same as any other unit of length, so you "use them" the same way. The easiest way to do unit conversions these days is through Google or Wolfram Alpha (wolframalpha.com). Go into either and type in something like:

1 parsec in meters

And you'll see how many meters a parsec is equal to. If you want to answer the question of how long something travelling at 100,000 miles per hour will take to reach the Earth starting from 10 parsecs away, type in smething like:

10 parsecs / (100,000 miles per hour)

(The answer is roughly 218731 years.)

Now, if you want to get a better feel for what a parsec means, you'd never see a meteor starting from 10 parsecs away - the nearest stars are only a couple of parsecs away, so the solar system (which contains just about all the meteors you're likely to see) is way smaller than that. Pluto is only about 0.0002 parsecs away. The edge of the Oort Cloud, which is believed to contain most of the solar system's comets, etc., is thought to have an edge of only about a quarter of a parsec. The distance between the Earth and the Sun is 5e-6 parsecs - that's 0.00005 parsecs