Beth, take a picture of all the Eheim parts you have, and we'll show you how to set everything up. I imagine you have the 2213 model (or something close like a 2217), and they're pretty easy to set up once you know how! I had the same problem as you because I bought mine used, but I didn't know which end the water came in/out, which made it a bit difficult.
If you know how to put it all together, then there are a couple tricks to getting it to flow properly. If you can't get water to go through, you can try two tactics. The first tactic involves sucking the water from the output hose, which can be gross (I don't like this method). The second method is to tilt the canister about 90 degrees forward (until its horizontal to the floor), and then tilting it straight back up. On older filters, this can take a while (I've spent 20 minutes trying to get one started up), but once it's started, it's usually pretty good for a while. If you don't overstock the tank, filter the gravel, and don't overfeed, you don't have to clean your filters all that often, so it's not a big problem!
Also, if you have the canister that is green (the 2213 to 2217 models), the water comes out of the top nozzle, and comes in through the bottom nozzle. You'll know when it's running properly when you don't hear any noise from the canister, even when tilting it around and such.
Hope that helps! If you need more assistance, take some pictures of the canister so we know what model you have and such!

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40 gallon - Future home of Abei Puffer
28 gallon - 1 Abei Puffer (Captain Abe)
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