which eheim canister filter are you talking about? There's a whole range you can be talk about...
But really, its pretty easy to set one up:
1. make sure all hoses and stuff are in place. Place the media in the canister body (if it is cleansed through pressure, place the coarse pad at the bottom with the bio balls - if you have any; then put the normal sponge in with ceramic noodles - if you have any; and the filter wool at the top by itself).... You may want to look at how the water comes in and work out where the coarse sponge should go - different models vary when placing media in...
2. Attach hoses, and attach inlet hose.
3. When everything is done, suck the outlet hose so the water can flow up the intake tube and fill the canister...
4. Place the outlet tube where you want it to go (while it is filling up)
5. As soon as the main body of the canister is full (water usually tends to go up the hose a bit); turn it on....
6. See how it goes, and rock the canister side to side to get expel the air bubbles that are trapped.
Hope that helps...